This patch renames gdbserver/win32-i386-low.c to
gdbserver/win32-low.c.  Well, actually, it is mostly a
ChangeLog entry, as it is useless to post a patch for the file move.
Patch 4 will then move the i386 specifics into a new
win32-i386-low.c, and add a win32-arm-low.c with ARM stuff.