core_unreal: Fix off by one buffer overwrite error.

core_unreal: Fix off by one buffer overwrite error.

Appending the ;2 to the user supplied ;1 uniqueid to create the ;2 version
if the user did not also supply an extra uniqueid for the ;2 channel
resulted in allocating a buffer that was one byte too small.

* Fix off by one error in ast_unreal_new_channels() when generating the ;2
uniqueid from the user suppled ;1 version.

* Pulled some long assignment lines from if tests to improve line break
readability in ast_unreal_new_channels().
........

Merged revisions 417119 from http://svn.asterisk.org/svn/asterisk/branches/12

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@417120 65c4cc65-6c06-0410-ace0-fbb531ad65f3