New stat structure.

* VFS and installed MFSes must be in sync before and after this change *

Use struct stat from NetBSD. It requires adding new STAT, FSTAT and LSTAT
syscalls. Libc modification is both backward and forward compatible.

Also new struct stat uses modern field sizes to avoid ABI
incompatibility, when we update uid_t, gid_t and company.
Exceptions are ino_t and off_t in old libc (though paddings added).

docs/UPDATING

@@ -1,3 +1,20 @@
+20110708
+        * VFS and installed MFSes must be in sync before and after this change *
+
+	You must update the GNU headers.
+	# cd /usr/src
+	# make gnu-includes
+
+	You must rebuild both MFS and VFS (including those one in the image).
+	Either make world or do the following:
+	# cd /usr/src/servers/mfs
+	# make install
+	# cd /usr/src/servers/vfs
+	# make install
+	# cd /usr/src/tools
+	# make hdboot
+	# shutdown -r now
+
 20110701:
 	# rm -rf /usr/include /usr/netbsd
 	# make etcfiles includes cleandepend depend gnu-includes