Speedup SAMUtils.compressedBasesToBytes for faster BAM file parsing

In my simple testcase (iterating through all sequences in one bam file) i saw that a large portion of the time was spent in SAMUtils.compressedBasesToBytes. Optimizing this function to use a Lookuptable made it about 50% faster, giving a speedup of 20% on the complete testcase.
I'm not sure how much faster it would make things but you might try re-ordering this method to just do the lookup without checking bounds and then catch the IndexOutOfBoundsException and rethrow with a more informative message.