mmap(2)-like allocation of buffer text on MS-Windows

[Eli Zaretskii]

Starting with trunk revision 117168, the MS-Windows build uses mmap(2)
emulation code, written by Fabrice Popineau, for allocating buffer
text.  This allows to stop using gmalloc.c and ralloc.c on this
platform, and thus get rid of the nasty problems with buffer text
relocation when large chunks of memory are allocated.  (There are
still a few other platforms that use ralloc.c, though.)

As a nice side-effect (due to changes in how dumped Lisp data is now
recorded on MS-Windows), the produced binary can now be stripped, so
that "make install-strip" should work.

I'd like to take this opportunity to thank Fabrice for his efforts,
and his endurance and perseverance during the long time this project
required.  Special thanks to Juanma for helping test the first
versions of the code.

Enjoy.