Implement predefined stdint macros

Add predefined stdint macros that match the given patterns:

U?INT{_,_FAST,_LEAST}{8,16,32,64}_{MAX,TYPE}
U?INT{PTR,MAX}_{MAX,TYPE}

http://reviews.llvm.org/D4141

Author: binji

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@211657 91177308-0d34-0410-b5e6-96231b3b80d8