Include assert.h manually in SourceLoc.h.
Include assert.h manually in SourceLoc.h.

On the BSDs when building with bootstrapping and therefore modules enabled,
this will result in a "declaration here is not visible" error. This is
_possibly_ because the assert implementation is not reexported from LLVM,
maybe due to libc differences. Regardless, this fixes the problem and
should be relatively inocuous to unconditionally include.

JGiola/swift,benlangmuir/swift,JGiola/swift,apple/swift,roambotics/swift,roambotics/swift,roambotics/swift,roambotics/swift,JGiola/swift,benlangmuir/swift,apple/swift,apple/swift,apple/swift,benlangmuir/swift,glessard/swift,JGiola/swift,JGiola/swift,glessard/swift,glessard/swift,apple/swift,glessard/swift,apple/swift,glessard/swift,JGiola/swift,benlangmuir/swift,glessard/swift,benlangmuir/swift,benlangmuir/swift,roambotics/swift,roambotics/swift