refactor: more understandable way to generate correct community version

The community version problem was introduced in Aug30, 2013

https://github.com/easemob/ejabberd/commit/8cbbe4a3ebe5f30c3cbf433e5a53ed3c2561bf0b#diff-67e997bcfdac55191033d57a16d1408a

in which the whitespace will make the command 'make rel' generate an incorrect package.

I do find it was partially fixed by a trivial shell command, 

https://github.com/easemob/ejabberd/commit/790201afc026c5c24596f5209694de5c135752c1#diff-67e997bcfdac55191033d57a16d1408a

and deem it should be fixed in a more understandable way.

The new command will also delete comma symbol which will mess the AC_INIT parameters.