Add hhbbc to gitignore.

Summary: Minor.
Closes https://github.com/facebook/hhvm/pull/4090

Reviewed By: @ptarjan

Differential Revision: D1646054

Signature: t1:1646054:1414570739:5128820bc61b046fade75e31af3fcc44e5369eff
Revert "Fixed iconv() error behaviour."

Summary: This reverts commit 0283fef5ed0713564cd98e9979dd9fa70ef7e574.

These make us incompatible with what is documented on http://php.net/manual/en/function.iconv.php . I'll put it back once I have a new runtime option.

Reviewed By: @paulbiss

Differential Revision: D1646146