Add parameters to makefont executable. (#61 on google code)

Original: http://code.google.com/p/freetype-gl/issues/detail?id=61

> The current implementation of the makefont executable could be a good base for own internal toolchains, that rely on freetype-gl. However a lot of interesting variables in makefont are hard coded. Those are:

> * the font name
> * the font size
> * the output header file name
> * the variable name used inside the font header.

> The attached patch implements command line parameters for those variables.
> Other potential interesting variables are the texture atlas resolution, the used license header and the glyph range but I didn't needed those yet and some maybe can be calculated.

> Currently the setup requires to set the font file name, the font size and the header file name. The font variable defaults to "font".

Here is the pull request you asked for.

Also it would be nice if you could merge the "Marcel Metz" and "Adrian Broher" to Marcel Metz in the contributors list.