ejabberd 14.05

Update to latest stable release, add options for brewed libraries, fix
compilation by bypassing ENV.cc.
Remove hardcoded clang

Just making sure that this fails on the test bot without hardcoding
clang.
Revert "Remove hardcoded clang"

This reverts commit 335bbdb05454994a5df2f0d0491a49017afe43ae.

The test bot does indeed fail on every OS without this.
Remove brewed versions of system libraries
ejabberd: add head
Remove brewed system library options all the way

I removed the dependencies but not these options earlier.
Remove hardcoded compiler
ejabberd 14.05

Homebrew's 'C compiler cannot create executables' bug workaround
ejabberd: update 14.05 bottle.