New source code extensions

This adds colors for the following extensions.

* C
  * .ii
* C++
  * .C
  * .cp
  * .cxx
  * .c++
  * .ii
  * .H
  * .hpp
  * .hxx
  * .h++
  * .tcc
* Fortran
  * .f
  * .for
  * .ftn
* Assembly
  * .s
  * .S
  * .sx
* Obj-C
  * .M