Fix confusion between RERR_NOSUPPORT and RERR_UNSUPPORTED for exit codes

that indicate a feature is not supported.  Two places that are normally
ifdefed out used RERR_UNSUPPORTED whereas one other place and errcode.h
used RERR_NOSUPPORT.  Changed them all to consistently use RERR_UNSUPPORTED.
The two things that had the bad values were #ifndef SUPPORT_LINKS and
#ifdef NO_INT64.  The former is probably for non-Unix operating systems
and the latter was at least on the default Unixware compiler.

errcode.h

@@ -3,7 +3,7 @@
 #define RERR_SYNTAX     1       /* syntax or usage error */
 #define RERR_PROTOCOL   2       /* protocol incompatibility */
 #define RERR_FILESELECT 3       /* errors selecting input/output files, dirs */
-#define RERR_NOSUPPORT  4       /* requested action not supported */
+#define RERR_UNSUPPORTED 4       /* requested action not supported */
 
 #define RERR_SOCKETIO   10      /* error in socket IO */
 #define RERR_FILEIO     11      /* error in file IO */

exclude.c

@@ -264,7 +264,7 @@ void send_exclude_list(int f)
 		if (exclude_list[i]->include) {
 			if (remote_version < 19) {
 				rprintf(FERROR,"remote rsync does not support include syntax - aborting\n");
-				exit_cleanup(RERR_NOSUPPORT);
+				exit_cleanup(RERR_UNSUPPORTED);
 			}
 			write_int(f,l+2);
 			write_buf(f,"+ ",2);