Implement the old mmap syscall for compat32, when COMPAT_43 option is

enabled. The syscall is used by FreeBSD 1.1.5.1 dynamic linker.

MFC after:	1 week

sys/compat/freebsd32/syscalls.master

@@ -168,7 +168,8 @@
 68	AUE_NULL	OBSOL	vwrite
 69	AUE_SBRK	NOPROTO	{ int sbrk(int incr); }
 70	AUE_SSTK	NOPROTO	{ int sstk(int incr); }
-71	AUE_MMAP	OBSOL	ommap
+71	AUE_MMAP	COMPAT|NOPROTO	{ int mmap(void *addr, int len, \
+				    int prot, int flags, int fd, int pos); }
 72	AUE_O_VADVISE	NOPROTO	{ int ovadvise(int anom); } vadvise \
 				    ovadvise_args int
 73	AUE_MUNMAP	NOPROTO	{ int munmap(void *addr, size_t len); }