mpileup: Added -x option to disable overlap detection
Updated tests and recovered output previously disabled for debugging
Merge branch fixmate of git://github.com/mp15/samtools

While merging: make the new man page subheading consistent with the
others; use sam_open("wb") to write a BAM file as before.  We may wish
to add an option to allow selection of the output format.
Merge branch 'develop' of github.com:samtools/samtools into develop
stats: Removed a too strict assert