w32: Use additional library libiberty.a

libiberty.a is part of MinGW and provides useful functions
like ffs (MinGW) and getopt (MinGW-w64).

It is needed for w64 compilations and allows simpler code for w32.

Cc: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: NStefan Weil <weil@mail.berlios.de>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

configure

@@ -474,7 +474,7 @@ if test "$mingw32" = "yes" ; then
   QEMU_CFLAGS="-DWIN32_LEAN_AND_MEAN -DWINVER=0x501 $QEMU_CFLAGS"
   # enable C99/POSIX format strings (needs mingw32-runtime 3.15 or later)
   QEMU_CFLAGS="-D__USE_MINGW_ANSI_STDIO=1 $QEMU_CFLAGS"
-  LIBS="-lwinmm -lws2_32 -liphlpapi $LIBS"
+  LIBS="-lwinmm -lws2_32 -liberty -liphlpapi $LIBS"
   prefix="c:/Program Files/Qemu"
   mandir="\${prefix}"
   datadir="\${prefix}"