*Improved Keyboard:
- Fixed crash when using Null keyboard handler
- Added support for meta keys
- Added support for {caps, num, scroll} lock.
*Small issues fixed in previous module:
- cellGifDec: Fixed wrong information of packet field in
cellGifDecReadHeader.
- cellGifDec: Set DataOutInfo.recordType as 1 since the output is always
an image.
- cellJpgDec: Set colorSpace as 3, until a better function is
implemented.
- cellJpgDec, cellPngDec: Added RGBA support.
*Changed layout of "Config > Settings" menu.
*Implemented 'cellGifDec', using 'sys_fs' to access the files and the
'stb_image' (stblib) library to decode GIF buffers to Raw-pixel buffers
that can be used as textures.
*Replace 'lodepng' and 'jpeg-compressor' libraries with 'stb_image' in
cellPngDec and cellJpgDec, respectively.
*Fixed minor issues in cellPngDec and cellJpgDec.
