Fix bitmask complement operation

The bitmask complement operation doesn't consider the max proc id which means
something like !{0} will be translated to {1,2,3,4,...,600,601,...,1023} on a
Linux system even though there aren't 600 processors on said system. This
change has the complement bitmask and-ed with the fullmask so that it will only
contain valid processors.

Differential Revision: http://reviews.llvm.org/D21245

llvm-svn: 272561