* configure.ac (BASEHEAD_LIST): Add _cygwin.h.
	* configure: Regenerate.

	* _cygwin.h: New file.
	* _mingw.h.in: Include _cygwin.h when building a Cygwin application.
	Allow building Cygwin applications even though _WIN32 isn't defined.
	* vadefs.h: Drop test for _WIN32 since it's done in _mingw.h.


git-svn-id: svn+ssh://svn.code.sf.net/p/mingw-w64/code/trunk@5133 4407c894-4637-0410-b4f5-ada5f102cad1