Problem: Win32: Cannot compile with XPM feature using VC2015
Solution: Add XPM libraries compiled with VC2015, and enable to build
gvim.exe which supports XPM using VC2015. (Ken Takata)
Problem: MingW needs build rule for included XPM files. Object directory
for 32 and 64 builds is the same, also for MSVC.
Solution: Add MingW build rule to use included XPM files. Add the CPU or
architecture to the object directory name. (Sergey Khorev)
