Use colorkey for 24bit BMP resources

  * needed to correctly display PCs/NPCs in PST's journal
Skip stacked items when sanitizing charges

Fixes some stacked items resetting to stack size 1 on load.
GUIScript: decide the scrollbar resource to use by GameCheck

you can still pass a BAM resref manually if you wish to override default behavior.
fixes BG1 spell selector.
Merge https://github.com/gemrb/gemrb
GLVideoRenderer: Shader source files. GLSLProgram now load shaders from text files. Automatically storing uniform locations during program creation.