RSX Debugger & cellFont improved

RSX Debugger:
*Better way to add name:value pairs to the tabs.
*Added some entries in the Settings/Texture/Lightning tabs.
*Experimental DisAsm.
*Support for previewing RGB textures (buggy!).
*Minor cleanups and improvements

cellFont:
*Added cellFontOpenFontMemory, cellFontOpenFontFile,
cellFontOpenFontset. They still need some modifications (e.g. bind these
functions to stblib/stb_truetype.h).