Use socklen_t if defined, or otherwise int. This tries to fix

warnings on platforms (e.g. AIX) where this type is defined and not
int.

configure.in

@@ -77,6 +77,7 @@ AC_TYPE_PID_T
 AC_TYPE_GETGROUPS
 AC_STRUCT_ST_RDEV
 AC_CHECK_TYPE([ino_t], [unsigned])
+AC_CHECK_TYPE([socklen_t], [int])
 
 AC_CACHE_CHECK([for errno in errno.h],rsync_cv_errno, [
     AC_TRY_COMPILE([#include <errno.h>],[int i = errno],

socket.c

@@ -227,13 +227,14 @@ static int open_socket_in(int type, int port, struct in_addr *address)
  */
 int is_a_socket(int fd)
 {
-	int v, l;
+	int v;
+	socklen_t l;
 	l = sizeof(int);
 
         /* Parameters to getsockopt, setsockopt etc are very
          * unstandardized across platforms, so don't be surprised if
-         * there are compiler warnings on e.g. SCO OpenSwerver.  It
-         * seems they all eventually get the right idea.
+         * there are compiler warnings on e.g. SCO OpenSwerver or AIX.
+         * It seems they all eventually get the right idea.
          *
          * Debian says: ``The fifth argument of getsockopt and
          * setsockopt is in reality an int [*] (and this is what BSD