Define _WIN32_IE for mingw builds. Fixing bustage.

Thanks to Sebastian Tusk <bugzilla.20.scyt@spamgourmet.com> for the patch.
Bug #297999 r=cls a=asa

toolkit/mozapps/update/src/updater/Makefile.in

@@ -68,6 +68,7 @@ ifndef GNU_CC
 RCFLAGS += -I$(srcdir)
 else
 RCFLAGS += --include-dir $(srcdir)
+DEFINES += -D_WIN32_IE=0x300
 endif
 endif