http: Use proper HTTP syntax for user agent string.

As noted by Nicolás Alvarez.

kdesrc-build

@@ -863,7 +863,7 @@ EOF
 
         # Trailing space adds the appropriate LWP info since the resolver is not
         # my custom coding anymore.
-        $ua->agent("kdesrc-build $versionNum ");
+        $ua->agent("kdesrc-build/$versionNum ");
 
         if ($proxy) {
             whisper ("Using proxy $proxy for FTP, HTTP downloads");