Speed up roundtrip syntax tests
Speed up roundtrip syntax tests

Running the unified diff is really slow, so first check if the strings
are identical. Speeds up the roundtrip stdlib test by 8x on my machine.

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