crt: Provide _aligned_msize function for all CRT import libraries

Function _aligned_msize() is available only in msvcr80+ and UCRT. It is not
available in msvcrt.dll system os library.

Now when the mingw-w64 aligned functions use same alignment and gap
calculation we can use mingw-w64 __mingw_aligned_msize() function as
implementation for CRT's _aligned_msize() function.

Signed-off-by: Martin Storsjö <martin@martin.st>