Move towlower and towupper to wctype.h and Implement it

This patch creates wctype.h and impelementat two functions
that belong to that header file towupper and towlower. These
functions are building blocks for wcscasecmp and wcsncasecmp
which are utilized by binutils.

The implementation for towlower and towupper seams to be complex
so this implementation is mimicking that of musl libc