Rewriting the same predicates over and over again is bad for code size and
code maintainence. Using the functions in <ctype.h> is generally unsafe
unless they are specified to be locale-independent (i.e. only isdigit and
isxdigit).
The next commit will try to clean up uses of <ctype.h> functions within Clang.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174765 91177308-0d34-0410-b5e6-96231b3b80d8