Implement CELL_GCM_TEXTURE_A1R5G5B5 & CELL_GCM_TEXTURE_A4R4G4B4

It is used by Terraria [BLES01938] .Missing background shown now though still wrong colors somehow.

http://www.emunewz.net/forum/showthread.php?tid=158739&pid=210220#pid210220

(Also reorganized bit in asc order from enum)