[Coverage] Fix function mapping record emission
[Coverage] Fix function mapping record emission

We emit an extra byte in the name field of function mapping records. The
extra null byte confuses llvm InstrProfReader, resulting in a loss of
coverage information.

We need execution tests to prevent this sort of issue from arising in
the future. Before that can happen, swift needs to start maintaining its
own branches of compiler-rt (this is SR-601).

Swift PR 1051, rdar://problem/24267336

(cherry picked from commit a476c2828ac7e0d3a761951f0363943ec9ff22ff)

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