Add MAP_ANONYMOUS.

Many operating systems also provide MAP_ANONYMOUS. It's not hard to
support this ourselves, we'd better add it to make it more likely for
applications to work out of the box.

Reviewed by:	alc (mman.h)

lib/libc/sys/mmap.2

@@ -28,7 +28,7 @@
 .\"	@(#)mmap.2	8.4 (Berkeley) 5/11/95
 .\" $FreeBSD$
 .\"
-.Dd July 26, 2009
+.Dd November 6, 2009
 .Dt MMAP 2
 .Os
 .Sh NAME
@@ -108,6 +108,10 @@ The
 argument is ignored.
 .\".It Dv MAP_FILE
 .\"Mapped from a regular file or character-special device memory.
+.It Dv MAP_ANONYMOUS
+This flag is identical to
+.Dv MAP_ANON
+and is provided for compatibility.
 .It Dv MAP_FIXED
 Do not permit the system to select a different address than the one
 specified.

sys/sys/mman.h

@@ -82,6 +82,9 @@
  */
 #define	MAP_FILE	 0x0000	/* map from file (default) */
 #define	MAP_ANON	 0x1000	/* allocated from memory, swap space */
+#ifndef _KERNEL
+#define	MAP_ANONYMOUS	 MAP_ANON /* For compatibility. */
+#endif /* !_KERNEL */
 
 /*
  * Extended flags