* made opencl kernel compilation+handling and oclraster_program creation thread-safe (sadly, no OpenCL implementation is actually capable of concurrently building OpenCL programs in the same context)
 * tccpp is now thread-safe -> updated tccpp submodule
 * all image functions in oclr_image_support.h are now #ifdef'ed for each image type, so that they're only compiled if the respective defines are set (which are only set for actually used image formats!) -> immense compilation speed increase
 * added locking functions to the opencl function (for external synchronization only)
 * the logger now uses a mutex instead of an atomic lock + cout is flushed too now (atomic lock and cout flushing didn't work out)
 * actually set/use the "valid" flag in oclraster_program (this signals if a oclraster_program has been processed and built; note that this doesn't signal if the build was successful)