update libraw to 0.11-beta3.

Changes (significant ones):

1) Fixed bug with half_size processing: if params.half_size is set, than params.four_color_rgb is set on postprocessing stage (that is right) and not returned back after postprocessing (that is wrong). So if you use half-mode and full-size in mixed sequence, it may result to postprocessing problems on some cameras.

2) AHD interpolation is refactored:
- on single-thread processing, entire processing (open-unpack-postprocess) is 5-10% faster than before.
- on multicore systems with OpenMP enabled, full processing pipeline is about 1.5 times faster on 4-core machine.

So, AHD part is MUCH faster.