resty: more improvements.

* made ngx.exit() an alias of os.exit().
* made the exit status code right for the wrapper process.
* require at least ngx_lua 0.9.12 to prevent memory bugs in older
  versions.
* suppressed a debugging output line.

util/ver

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 main_ver=1.7.4
-minor_ver=1rc1.1
+minor_ver=1rc1.2
 version=$main_ver.$minor_ver
 echo $version