vim: improve syntax highlighting for SIL attributes
vim: improve syntax highlighting for SIL attributes

Add rules to highlight the SIL attributes currently emitted by the swift
compiler.

jckarter/swift,tjw/swift,JGiola/swift,harlanhaskins/swift,practicalswift/swift,airspeedswift/swift,zisko/swift,allevato/swift,frootloops/swift,tkremenek/swift,ahoppen/swift,rudkx/swift,devincoughlin/swift,karwa/swift,devincoughlin/swift,jopamer/swift,benlangmuir/swift,JGiola/swift,devincoughlin/swift,gregomni/swift,sschiau/swift,parkera/swift,brentdax/swift,harlanhaskins/swift,CodaFi/swift,gregomni/swift,xedin/swift,alblue/swift,xedin/swift,stephentyrone/swift,glessard/swift,xedin/swift,ahoppen/swift,parkera/swift,parkera/swift,allevato/swift,roambotics/swift,nathawes/swift,harlanhaskins/swift,huonw/swift,JGiola/swift,devincoughlin/swift,karwa/swift,parkera/swift,amraboelela/swift,benlangmuir/swift,lorentey/swift,aschwaighofer/swift,jopamer/swift,CodaFi/swift,airspeedswift/swift,shahmishal/swift,huonw/swift,benlangmuir/swift,sschiau/swift,shajrawi/swift,brentdax/swift,huonw/swift,jmgc/swift,stephentyrone/swift,aschwaighofer/swift,hooman/swift,natecook1000/swift,shahmishal/swift,huonw/swift,roambotics/swift,ahoppen/swift,shahmishal/swift,huonw/swift,tjw/swift,gribozavr/swift,brentdax/swift,natecook1000/swift,huonw/swift,rudkx/swift,shajrawi/swift,tkremenek/swift,aschwaighofer/swift,ahoppen/swift,frootloops/swift,natecook1000/swift,lorentey/swift,austinzheng/swift,lorentey/swift,danielmartin/swift,gribozavr/swift,gribozavr/swift,jopamer/swift,xwu/swift,hooman/swift,atrick/swift,atrick/swift,practicalswift/swift,natecook1000/swift,gregomni/swift,gribozavr/swift,aschwaighofer/swift,devincoughlin/swift,harlanhaskins/swift,tjw/swift,austinzheng/swift,shahmishal/swift,xwu/swift,frootloops/swift,tjw/swift,karwa/swift,nathawes/swift,huonw/swift,hooman/swift,shajrawi/swift,CodaFi/swift,tkremenek/swift,brentdax/swift,zisko/swift,danielmartin/swift,brentdax/swift,amraboelela/swift,allevato/swift,lorentey/swift,tjw/swift,hooman/swift,sschiau/swift,danielmartin/swift,amraboelela/swift,allevato/swift,jckarter/swift,karwa/swift,practicalswift/swift,jmgc/swift,jopamer/swift,danielmartin/swift,JGiola/swift,sschiau/swift,JGiola/swift,parkera/swift,roambotics/swift,allevato/swift,roambotics/swift,apple/swift,amraboelela/swift,rudkx/swift,apple/swift,amraboelela/swift,glessard/swift,roambotics/swift,parkera/swift,allevato/swift,atrick/swift,lorentey/swift,xwu/swift,glessard/swift,sschiau/swift,tkremenek/swift,jopamer/swift,gribozavr/swift,stephentyrone/swift,glessard/swift,benlangmuir/swift,karwa/swift,sschiau/swift,rudkx/swift,parkera/swift,xedin/swift,natecook1000/swift,sschiau/swift,gregomni/swift,natecook1000/swift,xedin/swift,jckarter/swift,hooman/swift,stephentyrone/swift,CodaFi/swift,tkremenek/swift,sschiau/swift,devincoughlin/swift,ahoppen/swift,alblue/swift,jmgc/swift,airspeedswift/swift,zisko/swift,amraboelela/swift,jckarter/swift,zisko/swift,alblue/swift,nathawes/swift,CodaFi/swift,devincoughlin/swift,gribozavr/swift,natecook1000/swift,stephentyrone/swift,danielmartin/swift,jckarter/swift,airspeedswift/swift,stephentyrone/swift,lorentey/swift,hooman/swift,shahmishal/swift,austinzheng/swift,harlanhaskins/swift,karwa/swift,alblue/swift,gregomni/swift,alblue/swift,nathawes/swift,nathawes/swift,nathawes/swift,apple/swift,alblue/swift,stephentyrone/swift,aschwaighofer/swift,xwu/swift,tjw/swift,zisko/swift,frootloops/swift,xedin/swift,amraboelela/swift,parkera/swift,practicalswift/swift,practicalswift/swift,danielmartin/swift,xwu/swift,xwu/swift,aschwaighofer/swift,tkremenek/swift,austinzheng/swift,rudkx/swift,CodaFi/swift,jckarter/swift,shajrawi/swift,frootloops/swift,karwa/swift,xedin/swift,harlanhaskins/swift,apple/swift,austinzheng/swift,zisko/swift,practicalswift/swift,tkremenek/swift,shajrawi/swift,alblue/swift,shahmishal/swift,atrick/swift,practicalswift/swift,frootloops/swift,shajrawi/swift,jmgc/swift,austinzheng/swift,glessard/swift,shajrawi/swift,lorentey/swift,practicalswift/swift,tjw/swift,devincoughlin/swift,ahoppen/swift,harlanhaskins/swift,jmgc/swift,benlangmuir/swift,danielmartin/swift,benlangmuir/swift,shahmishal/swift,aschwaighofer/swift,CodaFi/swift,lorentey/swift,rudkx/swift,jopamer/swift,zisko/swift,shahmishal/swift,glessard/swift,atrick/swift,gribozavr/swift,xwu/swift,gribozavr/swift,xedin/swift,hooman/swift,JGiola/swift,jckarter/swift,brentdax/swift,apple/swift,nathawes/swift,gregomni/swift,apple/swift,airspeedswift/swift,frootloops/swift,austinzheng/swift,roambotics/swift,jmgc/swift,karwa/swift,shajrawi/swift,atrick/swift,airspeedswift/swift,airspeedswift/swift,jopamer/swift,brentdax/swift,allevato/swift,jmgc/swift