[Lex] Use clang::isIdentifierBody instead of checking for '_' separately.
[Lex] Use clang::isIdentifierBody instead of checking for '_' separately.

Also, use 'isHexDigit' instead of the built-in 'isxdigit' for consistency,
even though 'isxdigit' is locale-independent.

No intended functionality change.

Swift SVN r31139

ben-ng/swift,benlangmuir/swift,roambotics/swift,danielmartin/swift,Jnosh/swift,gregomni/swift,kperryua/swift,KrishMunot/swift,frootloops/swift,adrfer/swift,atrick/swift,khizkhiz/swift,xwu/swift,kentya6/swift,gribozavr/swift,rudkx/swift,djwbrown/swift,aschwaighofer/swift,xedin/swift,codestergit/swift,airspeedswift/swift,frootloops/swift,xwu/swift,modocache/swift,modocache/swift,therealbnut/swift,xwu/swift,codestergit/swift,adrfer/swift,therealbnut/swift,slavapestov/swift,parkera/swift,practicalswift/swift,jckarter/swift,therealbnut/swift,apple/swift,amraboelela/swift,JGiola/swift,sschiau/swift,gottesmm/swift,gmilos/swift,swiftix/swift,uasys/swift,bitjammer/swift,rudkx/swift,huonw/swift,glessard/swift,MukeshKumarS/Swift,KrishMunot/swift,jtbandes/swift,amraboelela/swift,roambotics/swift,Jnosh/swift,huonw/swift,swiftix/swift.old,zisko/swift,milseman/swift,alblue/swift,djwbrown/swift,tinysun212/swift-windows,Ivacker/swift,IngmarStein/swift,apple/swift,huonw/swift,shahmishal/swift,mightydeveloper/swift,sschiau/swift,harlanhaskins/swift,uasys/swift,devincoughlin/swift,devincoughlin/swift,calebd/swift,glessard/swift,brentdax/swift,jopamer/swift,lorentey/swift,nathawes/swift,jckarter/swift,allevato/swift,shajrawi/swift,slavapestov/swift,calebd/swift,russbishop/swift,nathawes/swift,austinzheng/swift,Jnosh/swift,khizkhiz/swift,shajrawi/swift,kentya6/swift,kstaring/swift,cbrentharris/swift,tardieu/swift,tardieu/swift,harlanhaskins/swift,OscarSwanros/swift,zisko/swift,sschiau/swift,cbrentharris/swift,kperryua/swift,Ivacker/swift,huonw/swift,xedin/swift,allevato/swift,swiftix/swift.old,russbishop/swift,swiftix/swift,xedin/swift,CodaFi/swift,tinysun212/swift-windows,slavapestov/swift,tardieu/swift,tkremenek/swift,codestergit/swift,brentdax/swift,lorentey/swift,alblue/swift,atrick/swift,danielmartin/swift,gmilos/swift,atrick/swift,MukeshKumarS/Swift,khizkhiz/swift,swiftix/swift,tjw/swift,parkera/swift,emilstahl/swift,adrfer/swift,SwiftAndroid/swift,natecook1000/swift,practicalswift/swift,LeoShimonaka/swift,mightydeveloper/swift,codestergit/swift,ken0nek/swift,emilstahl/swift,LeoShimonaka/swift,khizkhiz/swift,huonw/swift,dduan/swift,kusl/swift,kusl/swift,ben-ng/swift,harlanhaskins/swift,johnno1962d/swift,ben-ng/swift,aschwaighofer/swift,harlanhaskins/swift,alblue/swift,shahmishal/swift,practicalswift/swift,KrishMunot/swift,roambotics/swift,allevato/swift,lorentey/swift,alblue/swift,uasys/swift,jckarter/swift,tkremenek/swift,manavgabhawala/swift,kstaring/swift,cbrentharris/swift,JaSpa/swift,sdulal/swift,ahoppen/swift,austinzheng/swift,jopamer/swift,hooman/swift,nathawes/swift,therealbnut/swift,LeoShimonaka/swift,sdulal/swift,sdulal/swift,roambotics/swift,tardieu/swift,tkremenek/swift,atrick/swift,modocache/swift,khizkhiz/swift,natecook1000/swift,slavapestov/swift,shajrawi/swift,brentdax/swift,jmgc/swift,bitjammer/swift,natecook1000/swift,shahmishal/swift,Ivacker/swift,tjw/swift,tjw/swift,felix91gr/swift,calebd/swift,shahmishal/swift,dduan/swift,felix91gr/swift,atrick/swift,gregomni/swift,amraboelela/swift,ken0nek/swift,slavapestov/swift,rudkx/swift,mightydeveloper/swift,felix91gr/swift,ben-ng/swift,kentya6/swift,modocache/swift,SwiftAndroid/swift,Ivacker/swift,shahmishal/swift,allevato/swift,roambotics/swift,parkera/swift,adrfer/swift,arvedviehweger/swift,jtbandes/swift,JaSpa/swift,harlanhaskins/swift,milseman/swift,Ivacker/swift,frootloops/swift,arvedviehweger/swift,stephentyrone/swift,kusl/swift,swiftix/swift.old,apple/swift,djwbrown/swift,amraboelela/swift,SwiftAndroid/swift,kstaring/swift,sschiau/swift,stephentyrone/swift,russbishop/swift,khizkhiz/swift,ahoppen/swift,slavapestov/swift,modocache/swift,Ivacker/swift,slavapestov/swift,jtbandes/swift,return/swift,emilstahl/swift,IngmarStein/swift,cbrentharris/swift,tardieu/swift,jopamer/swift,tardieu/swift,karwa/swift,danielmartin/swift,kusl/swift,felix91gr/swift,cbrentharris/swift,manavgabhawala/swift,JGiola/swift,shahmishal/swift,CodaFi/swift,JaSpa/swift,KrishMunot/swift,kperryua/swift,russbishop/swift,dduan/swift,huonw/swift,uasys/swift,khizkhiz/swift,airspeedswift/swift,JGiola/swift,OscarSwanros/swift,arvedviehweger/swift,deyton/swift,SwiftAndroid/swift,mightydeveloper/swift,milseman/swift,gregomni/swift,benlangmuir/swift,CodaFi/swift,amraboelela/swift,sschiau/swift,shajrawi/swift,OscarSwanros/swift,felix91gr/swift,nathawes/swift,bitjammer/swift,benlangmuir/swift,manavgabhawala/swift,felix91gr/swift,devincoughlin/swift,milseman/swift,johnno1962d/swift,zisko/swift,JGiola/swift,kusl/swift,practicalswift/swift,gribozavr/swift,harlanhaskins/swift,MukeshKumarS/Swift,danielmartin/swift,deyton/swift,swiftix/swift,cbrentharris/swift,deyton/swift,hughbe/swift,gribozavr/swift,gribozavr/swift,tkremenek/swift,JaSpa/swift,uasys/swift,bitjammer/swift,LeoShimonaka/swift,kstaring/swift,parkera/swift,kstaring/swift,lorentey/swift,austinzheng/swift,airspeedswift/swift,sschiau/swift,MukeshKumarS/Swift,IngmarStein/swift,roambotics/swift,arvedviehweger/swift,mightydeveloper/swift,xedin/swift,hughbe/swift,tjw/swift,rudkx/swift,gregomni/swift,ken0nek/swift,kusl/swift,xedin/swift,tardieu/swift,frootloops/swift,stephentyrone/swift,karwa/swift,cbrentharris/swift,manavgabhawala/swift,swiftix/swift.old,zisko/swift,dduan/swift,KrishMunot/swift,practicalswift/swift,CodaFi/swift,glessard/swift,kstaring/swift,djwbrown/swift,IngmarStein/swift,shahmishal/swift,Jnosh/swift,johnno1962d/swift,adrfer/swift,xwu/swift,jtbandes/swift,hughbe/swift,kentya6/swift,kperryua/swift,mightydeveloper/swift,ben-ng/swift,jtbandes/swift,karwa/swift,JaSpa/swift,jmgc/swift,zisko/swift,calebd/swift,deyton/swift,codestergit/swift,xwu/swift,JaSpa/swift,johnno1962d/swift,jopamer/swift,aschwaighofer/swift,sdulal/swift,ben-ng/swift,arvedviehweger/swift,natecook1000/swift,SwiftAndroid/swift,nathawes/swift,tkremenek/swift,djwbrown/swift,apple/swift,kperryua/swift,gottesmm/swift,sdulal/swift,return/swift,gregomni/swift,modocache/swift,hughbe/swift,johnno1962d/swift,ahoppen/swift,gottesmm/swift,adrfer/swift,brentdax/swift,ken0nek/swift,jopamer/swift,apple/swift,huonw/swift,jckarter/swift,hughbe/swift,gribozavr/swift,emilstahl/swift,sdulal/swift,karwa/swift,mightydeveloper/swift,austinzheng/swift,gribozavr/swift,Jnosh/swift,russbishop/swift,codestergit/swift,austinzheng/swift,jmgc/swift,MukeshKumarS/Swift,tkremenek/swift,KrishMunot/swift,allevato/swift,djwbrown/swift,lorentey/swift,hooman/swift,bitjammer/swift,hooman/swift,karwa/swift,gribozavr/swift,brentdax/swift,parkera/swift,CodaFi/swift,therealbnut/swift,jckarter/swift,gmilos/swift,swiftix/swift.old,glessard/swift,calebd/swift,airspeedswift/swift,tjw/swift,danielmartin/swift,felix91gr/swift,natecook1000/swift,return/swift,bitjammer/swift,return/swift,xwu/swift,shajrawi/swift,xedin/swift,LeoShimonaka/swift,IngmarStein/swift,harlanhaskins/swift,tinysun212/swift-windows,mightydeveloper/swift,therealbnut/swift,amraboelela/swift,natecook1000/swift,ben-ng/swift,hughbe/swift,aschwaighofer/swift,Jnosh/swift,KrishMunot/swift,tjw/swift,jckarter/swift,tkremenek/swift,therealbnut/swift,aschwaighofer/swift,sdulal/swift,OscarSwanros/swift,apple/swift,alblue/swift,devincoughlin/swift,deyton/swift,brentdax/swift,rudkx/swift,calebd/swift,deyton/swift,jmgc/swift,sschiau/swift,jmgc/swift,return/swift,hooman/swift,xedin/swift,gottesmm/swift,parkera/swift,hooman/swift,parkera/swift,airspeedswift/swift,arvedviehweger/swift,jopamer/swift,ahoppen/swift,practicalswift/swift,swiftix/swift.old,tinysun212/swift-windows,dreamsxin/swift,kentya6/swift,manavgabhawala/swift,milseman/swift,ken0nek/swift,manavgabhawala/swift,gmilos/swift,SwiftAndroid/swift,zisko/swift,stephentyrone/swift,hughbe/swift,jtbandes/swift,russbishop/swift,swiftix/swift.old,danielmartin/swift,devincoughlin/swift,devincoughlin/swift,airspeedswift/swift,gottesmm/swift,CodaFi/swift,milseman/swift,austinzheng/swift,gmilos/swift,gmilos/swift,stephentyrone/swift,benlangmuir/swift,kperryua/swift,stephentyrone/swift,calebd/swift,benlangmuir/swift,russbishop/swift,ahoppen/swift,OscarSwanros/swift,modocache/swift,lorentey/swift,LeoShimonaka/swift,stephentyrone/swift,zisko/swift,shahmishal/swift,JaSpa/swift,uasys/swift,IngmarStein/swift,jtbandes/swift,Jnosh/swift,airspeedswift/swift,kentya6/swift,kusl/swift,uasys/swift,jmgc/swift,shajrawi/swift,Ivacker/swift,glessard/swift,atrick/swift,frootloops/swift,swiftix/swift,swiftix/swift.old,alblue/swift,hooman/swift,karwa/swift,johnno1962d/swift,JGiola/swift,devincoughlin/swift,MukeshKumarS/Swift,emilstahl/swift,Ivacker/swift,benlangmuir/swift,karwa/swift,jmgc/swift,kperryua/swift,bitjammer/swift,xedin/swift,johnno1962d/swift,codestergit/swift,gottesmm/swift,emilstahl/swift,alblue/swift,ken0nek/swift,kentya6/swift,CodaFi/swift,swiftix/swift,frootloops/swift,nathawes/swift,dduan/swift,LeoShimonaka/swift,xwu/swift,hooman/swift,allevato/swift,natecook1000/swift,dduan/swift,kentya6/swift,dduan/swift,OscarSwanros/swift,jckarter/swift,milseman/swift,danielmartin/swift,ahoppen/swift,arvedviehweger/swift,gribozavr/swift,aschwaighofer/swift,jopamer/swift,adrfer/swift,MukeshKumarS/Swift,glessard/swift,amraboelela/swift,tinysun212/swift-windows,djwbrown/swift,brentdax/swift,return/swift,tinysun212/swift-windows,cbrentharris/swift,gottesmm/swift,tjw/swift,SwiftAndroid/swift,kstaring/swift,aschwaighofer/swift,LeoShimonaka/swift,sschiau/swift,nathawes/swift,tinysun212/swift-windows,practicalswift/swift,practicalswift/swift,devincoughlin/swift,emilstahl/swift,ken0nek/swift,swiftix/swift,kusl/swift,gmilos/swift,OscarSwanros/swift,frootloops/swift,karwa/swift,lorentey/swift,sdulal/swift,manavgabhawala/swift,emilstahl/swift,deyton/swift,shajrawi/swift,dreamsxin/swift,rudkx/swift,austinzheng/swift,return/swift,parkera/swift,IngmarStein/swift,JGiola/swift,gregomni/swift,lorentey/swift,allevato/swift,shajrawi/swift