Some cleanups and fixes.
Separates the logic on transform type selection previously spread out over a number of files into a separate function. Currently the tx_type field in b_mode_info is not used, but still left in there to eventually use for signaling the transform type in the bitstream. Also, now for tx_type = DCT_DCT, the regular integer DCT is used, as opposed to the floating point DCT used in conjuction with hybrid transform. Results change somewhat due to the transform change, but are within reasonable limits. The hd/std-hd sets are slightly up, while derf/yt are slightly down. Change-Id: I5776840c2239ca2da31ca6cfd7fd1148dc5f9e0f