New formula: GCC 4.9.
New formula: GCC 4.9.

* Development snapshot of GCC trunk, version 4.9.
* Head tracking trunk.
* Add caveat to warn about development snapshot.
* Correctly detect machine type.

DomT4/homebrew-versions,coeligena/homebrew-verscustomized,jimhe/homebrew-versions,Ashton-W/homebrew-versions,heuermh/homebrew-versions,UniqMartin/homebrew-versions