[Diagnostics] Use constant strings to avoid use after free.
[Diagnostics] Use constant strings to avoid use after free.

Using std::string in the function signature copies the constant string
into a stack allocated copy, which is the one referenced by the
StringRef that DiagnosticInfo stores. when the stack is abandoned, the
string seems to be modificed in VC++, which makes the test fail in
Windows.

Using const char * in the signature avoids the std::string creation, and
StringRef will refer to the static data instead.

aschwaighofer/swift,gribozavr/swift,lorentey/swift,karwa/swift,tkremenek/swift,xwu/swift,harlanhaskins/swift,airspeedswift/swift,parkera/swift,jckarter/swift,rudkx/swift,stephentyrone/swift,xwu/swift,roambotics/swift,stephentyrone/swift,parkera/swift,jckarter/swift,airspeedswift/swift,karwa/swift,karwa/swift,gribozavr/swift,gribozavr/swift,apple/swift,CodaFi/swift,lorentey/swift,JGiola/swift,tkremenek/swift,allevato/swift,gregomni/swift,benlangmuir/swift,rudkx/swift,xwu/swift,karwa/swift,lorentey/swift,lorentey/swift,glessard/swift,stephentyrone/swift,lorentey/swift,allevato/swift,atrick/swift,tkremenek/swift,CodaFi/swift,gribozavr/swift,CodaFi/swift,tkremenek/swift,xwu/swift,ahoppen/swift,harlanhaskins/swift,nathawes/swift,airspeedswift/swift,glessard/swift,apple/swift,jmgc/swift,apple/swift,jmgc/swift,roambotics/swift,jmgc/swift,JGiola/swift,harlanhaskins/swift,jckarter/swift,ahoppen/swift,allevato/swift,gribozavr/swift,glessard/swift,harlanhaskins/swift,karwa/swift,atrick/swift,atrick/swift,nathawes/swift,harlanhaskins/swift,parkera/swift,parkera/swift,benlangmuir/swift,lorentey/swift,parkera/swift,aschwaighofer/swift,CodaFi/swift,parkera/swift,hooman/swift,parkera/swift,aschwaighofer/swift,airspeedswift/swift,glessard/swift,gregomni/swift,apple/swift,ahoppen/swift,rudkx/swift,JGiola/swift,karwa/swift,CodaFi/swift,airspeedswift/swift,apple/swift,benlangmuir/swift,glessard/swift,rudkx/swift,hooman/swift,nathawes/swift,jckarter/swift,lorentey/swift,jmgc/swift,benlangmuir/swift,stephentyrone/swift,allevato/swift,jmgc/swift,gregomni/swift,tkremenek/swift,glessard/swift,JGiola/swift,jckarter/swift,lorentey/swift,CodaFi/swift,allevato/swift,JGiola/swift,hooman/swift,nathawes/swift,nathawes/swift,nathawes/swift,jckarter/swift,benlangmuir/swift,CodaFi/swift,xwu/swift,apple/swift,atrick/swift,xwu/swift,ahoppen/swift,harlanhaskins/swift,aschwaighofer/swift,karwa/swift,aschwaighofer/swift,ahoppen/swift,karwa/swift,gribozavr/swift,ahoppen/swift,aschwaighofer/swift,benlangmuir/swift,stephentyrone/swift,airspeedswift/swift,parkera/swift,hooman/swift,atrick/swift,gribozavr/swift,jckarter/swift,stephentyrone/swift,jmgc/swift,jmgc/swift,rudkx/swift,allevato/swift,hooman/swift,tkremenek/swift,harlanhaskins/swift,atrick/swift,roambotics/swift,JGiola/swift,hooman/swift,roambotics/swift,gribozavr/swift,hooman/swift,allevato/swift,gregomni/swift,gregomni/swift,gregomni/swift,stephentyrone/swift,roambotics/swift,tkremenek/swift,xwu/swift,nathawes/swift,rudkx/swift,roambotics/swift,airspeedswift/swift,aschwaighofer/swift