configure: remove Cygwin

The Cygwin target is really compiling for native Win32 with -mno-cygwin.
Except, GCC 4.7.0 has finally removed the long deprecated -mno-cygwin
option, and that happened about five years ago.

Let it rest in peace.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

bsd-user/mmap.c

@@ -199,12 +199,7 @@ static int mmap_frag(abi_ulong real_start,
     return 0;
 }
 
-#if defined(__CYGWIN__)
-/* Cygwin doesn't have a whole lot of address space.  */
-static abi_ulong mmap_next_start = 0x18000000;
-#else
 static abi_ulong mmap_next_start = 0x40000000;
-#endif
 
 unsigned long last_brk;
 

configure

@@ -553,12 +553,6 @@ fi
 HOST_VARIANT_DIR=""
 
 case $targetos in
-CYGWIN*)
-  mingw32="yes"
-  QEMU_CFLAGS="-mno-cygwin $QEMU_CFLAGS"
-  audio_possible_drivers="sdl"
-  audio_drv_list="sdl"
-;;
 MINGW32*)
   mingw32="yes"
   hax="yes"