Fix build error on GCC/Clang + STLport.

* Add missing #include <cctype> since STLport has different
  implementation that <cctype> won't be included indirectly.

* Add missing cast from enum value to unsigned int. Otherwise
  GCC 4.6 will bump a compile error w/ -pedantic flag.

* Backport upstream r178356.

    commit 71246fb8
    Author: Matt Arsenault <Matthew.Arsenault@amd.com>
    Date:   Fri Mar 29 18:48:45 2013 +0000

    Build fixes for STLPort + GCC

    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178356 91177308-0d34-0410-b5e6-96231b3b80d8

Cherry-picked from release_32 branch.

Change-Id: I1079e402a6df8b921c71d22ef19a4779637c408f