cross/mingw-w64-x86_64-headers: import mingw-w64-x86_64-headers-5.0.4

Mingw-w64 is an advancement of the original mingw.org project,
created to support the GCC compiler on Windows systems. It has
forked it in 2007 in order to provide support for 64 bits and new
APIs. It has since then gained widespread use and distribution.

This package provides headers for mingw-w64 x86_64 target.

(ryoon)