Add a -verify-linetable LLVM option.
Add a -verify-linetable LLVM option.

While stepping through Swift programs in LLDB I noticed that sometimes
the line table entries go like this:

  foo(bar(baz)) // Some auxiliary code for the entire expression.
  ^

  foo(bar(baz))
      ^

  foo(bar(baz)) // And then back again for that actual call to foo.
  ^

This verification step is aimed at identifying situations like this so
they can be fixed.

parkera/swift,tkremenek/swift,benlangmuir/swift,jckarter/swift,shajrawi/swift,jckarter/swift,ahoppen/swift,stephentyrone/swift,JGiola/swift,allevato/swift,shahmishal/swift,harlanhaskins/swift,sschiau/swift,jmgc/swift,airspeedswift/swift,practicalswift/swift,benlangmuir/swift,airspeedswift/swift,devincoughlin/swift,hooman/swift,shahmishal/swift,airspeedswift/swift,shajrawi/swift,shajrawi/swift,lorentey/swift,tkremenek/swift,jmgc/swift,apple/swift,amraboelela/swift,danielmartin/swift,benlangmuir/swift,apple/swift,karwa/swift,brentdax/swift,nathawes/swift,lorentey/swift,devincoughlin/swift,austinzheng/swift,ahoppen/swift,devincoughlin/swift,roambotics/swift,danielmartin/swift,roambotics/swift,glessard/swift,benlangmuir/swift,karwa/swift,JGiola/swift,gregomni/swift,airspeedswift/swift,alblue/swift,devincoughlin/swift,lorentey/swift,alblue/swift,CodaFi/swift,shajrawi/swift,CodaFi/swift,xwu/swift,karwa/swift,rudkx/swift,roambotics/swift,lorentey/swift,gregomni/swift,austinzheng/swift,jmgc/swift,amraboelela/swift,roambotics/swift,xedin/swift,alblue/swift,brentdax/swift,practicalswift/swift,roambotics/swift,allevato/swift,brentdax/swift,stephentyrone/swift,hooman/swift,aschwaighofer/swift,tkremenek/swift,amraboelela/swift,atrick/swift,jckarter/swift,parkera/swift,aschwaighofer/swift,nathawes/swift,parkera/swift,lorentey/swift,xwu/swift,stephentyrone/swift,lorentey/swift,karwa/swift,harlanhaskins/swift,jckarter/swift,nathawes/swift,sschiau/swift,danielmartin/swift,gribozavr/swift,aschwaighofer/swift,lorentey/swift,harlanhaskins/swift,lorentey/swift,shahmishal/swift,austinzheng/swift,sschiau/swift,nathawes/swift,austinzheng/swift,jckarter/swift,alblue/swift,shajrawi/swift,shahmishal/swift,brentdax/swift,parkera/swift,apple/swift,allevato/swift,airspeedswift/swift,tkremenek/swift,shahmishal/swift,shahmishal/swift,sschiau/swift,xwu/swift,gribozavr/swift,apple/swift,glessard/swift,alblue/swift,CodaFi/swift,aschwaighofer/swift,gregomni/swift,parkera/swift,xwu/swift,jmgc/swift,practicalswift/swift,devincoughlin/swift,karwa/swift,rudkx/swift,xwu/swift,glessard/swift,alblue/swift,sschiau/swift,harlanhaskins/swift,ahoppen/swift,CodaFi/swift,hooman/swift,parkera/swift,xwu/swift,allevato/swift,jmgc/swift,glessard/swift,atrick/swift,stephentyrone/swift,tkremenek/swift,karwa/swift,danielmartin/swift,shajrawi/swift,shajrawi/swift,devincoughlin/swift,practicalswift/swift,harlanhaskins/swift,devincoughlin/swift,austinzheng/swift,CodaFi/swift,parkera/swift,parkera/swift,danielmartin/swift,gribozavr/swift,nathawes/swift,practicalswift/swift,allevato/swift,hooman/swift,practicalswift/swift,xedin/swift,brentdax/swift,jckarter/swift,practicalswift/swift,atrick/swift,rudkx/swift,gribozavr/swift,xwu/swift,tkremenek/swift,rudkx/swift,stephentyrone/swift,aschwaighofer/swift,roambotics/swift,JGiola/swift,atrick/swift,shahmishal/swift,atrick/swift,CodaFi/swift,apple/swift,amraboelela/swift,aschwaighofer/swift,austinzheng/swift,rudkx/swift,glessard/swift,hooman/swift,jmgc/swift,ahoppen/swift,xedin/swift,JGiola/swift,stephentyrone/swift,hooman/swift,harlanhaskins/swift,sschiau/swift,shajrawi/swift,nathawes/swift,ahoppen/swift,karwa/swift,alblue/swift,austinzheng/swift,xedin/swift,allevato/swift,aschwaighofer/swift,brentdax/swift,gregomni/swift,xedin/swift,hooman/swift,atrick/swift,CodaFi/swift,gregomni/swift,gregomni/swift,harlanhaskins/swift,allevato/swift,JGiola/swift,benlangmuir/swift,amraboelela/swift,amraboelela/swift,apple/swift,jckarter/swift,danielmartin/swift,shahmishal/swift,devincoughlin/swift,JGiola/swift,glessard/swift,tkremenek/swift,brentdax/swift,nathawes/swift,sschiau/swift,gribozavr/swift,gribozavr/swift,benlangmuir/swift,ahoppen/swift,jmgc/swift,sschiau/swift,rudkx/swift,gribozavr/swift,xedin/swift,gribozavr/swift,xedin/swift,airspeedswift/swift,amraboelela/swift,airspeedswift/swift,xedin/swift,karwa/swift,stephentyrone/swift,practicalswift/swift,danielmartin/swift