gcc4x: adjust default language set

Now that these compilers are available for use by Homebrew, we need a
standard minimum set of languages that will be supported.

* Always build with C++ - Homebrew assumes this will always be
  available, and this is also really common. (See mxcl/homebrew#24274)
* Also build ObjC/ObjC++ - some packages like vim, glib need this

Closes #277.

Signed-off-by: Misty De Meo <mistydemeo@gmail.com>