bsd/xdr: Silence uninitialized use warnings with -O3

Gcc comaplins about attempt to read 'size' via dereferencing a pointer
in xdr_u_int() in case xdrs->x_op == XDR_ENCODE.  However, in this
case the size will be set from the switch case inside xdr_string()
before xdr_u_int() is invoked. I think it's spurious because the
code clearly assumes that xdrs->x_op cannot change between these two
execution points.

Let's initialize 'size' to 0 to make gcc happy.

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

bsd/sys/xdr/xdr.c

@@ -617,7 +617,7 @@ bool_t
 xdr_string(XDR *xdrs, char **cpp, u_int maxsize)
 {
 	char *sp = *cpp;  /* sp is the actual string pointer */
-	u_int size;
+	u_int size = 0;
 	u_int nodesize;
 
 	/*