Honor DESTDIR in w32api and mingw

[Charles Wilson]

Corinna Vinschen wrote:

> The Mingw developers should approve mingw stuff, usually.

Then any interested parties should read the ongoing thread here:
http://thread.gmane.org/gmane.comp.gnu.mingw.devel/3478

IMO, Keith is being unreasonable about "if DESTDIR doesn't work on
win32, we shouldn't add support for it even for those platforms where it
will work".  He's graciously allowed that this patch could go in, IF I
convince the automake and autoconf developers to completely redesign the
 way DESTDIR works so that it accommodates X: paths.

--
Chuck