* fixed image and framebufer reading/writing (all pointers are now being correctly offset by the image header size)
 * increased image header size to 32 bytes (24 padding bytes); this is necessary for correct alignment with all types (largest possible type: 64-bit RGBA = 32 bytes)
 * added preliminary runtime kernel reloading support (still wip, but functional; note that this will always require specific handling on the users side)
 * fixed oclraster_images/oclraster_framebuffer parsing when no access qualifier is specified, but a format hint is
 * fixed depth testing in the rasterization stage (ignore negative depth)
 * some cleanup/code unification in oclr_image_support.h: all nearest filtering functions with 2D texture coordinates now call a corresponding nearest filtering function that takes a 1D offset/index into the texture (can also be used from the outside!)
 * made oclr_simple sample compatible to runtime kernel reloading + some cleanup
 * added debug user programs to oclr_simple