(LINUX_MAP_SHARED_DOES_WORK): Define for kernel

version after 2.0.
(UNEXEC_USE_MAP_PRIVATE): Don't define if
LINUX_MAP_SHARED_DOES_WORK.

src/s/gnu-linux.h

@@ -47,6 +47,9 @@ Boston, MA 02111-1307, USA.  */
 #if LINUX_VERSION_CODE > 0x10200
 #define LINUX_SIGIO_DOES_WORK
 #endif /* LINUX_VERSION_CODE > 0x10200 */
+#if LINUX_VERSION_CODE >= 0x20000
+#define LINUX_MAP_SHARED_DOES_WORK
+#endif /* LINUX_VERSION_CODE >= 0x20000 */
 #endif /* HAVE_LINUX_VERSION_H */
 #endif /* emacs */
 #endif /* NOT_C_CODE */
@@ -243,8 +246,10 @@ Boston, MA 02111-1307, USA.  */
 
 #ifdef __ELF__
 #define UNEXEC unexelf.o
+#ifndef LINUX_MAP_SHARED_DOES_WORK
 #define UNEXEC_USE_MAP_PRIVATE
 #endif
+#endif
 
 #ifdef LINUX_QMAGIC