Reduced the number of realloc calls zlib_mem_inflate(), while
hopefully not overallocating much either.

Forcibly set block->alloc field when decompressing from gzip or
bzip2. This caused issues in scramble, but doesn't seem to in samtools
due to no ability to set compression level higher. Fixing it here just
incase though.
Merge pull request #62, minor CRAM updates
synced_reader: New bcf_sr_region_done macro
Check cram_eof() before calling cram_close()

...rather than after the file descriptor is gone.  Fixes #65.
bcf_translate: Catch unchecked errors
More sensible Quals of matching bases in overlaps
Ignore operation-not-supported errors in fd_flush

to prevent hts_close() errors on Mac OS X.