Miscellaneous trivia and minor fixes

[jmarshall]

Several minor fixes that you may wish to select from and squash:

• Remove remnants of now unused HTS_HAVE_NEON. This has already been cherry-picked into pysam, as we print it out in the logs so these remnants could have caused confusion.

• Remove remnants of NUMERIC_VERSION, unused since #1226. Eventually with a soversion bump you may revisit how MACH_O_CURRENT_VERSION is set and perhaps set it from version.sh numeric, so that code in version.sh has been left. (We will soon not ship htslib/version.sh in pysam so will need to apply something like this to our htslib/Makefile whether htslib does or not.)

• Document primarily MM/ML tags — rather than the draft Mm/Ml — and fix base-mod-related typos.

• Avoid a “PRId64 used with size_t” warning. This change adds a cast to the always-run if() condition as well as to the almost-never-run diagnostic printing, so deserves more review than the rest of this PR.

• Install annot-tsv.1 man page and alphabetise annot-tsv rules. I thought perhaps the maintainers would rename this to something more appealing — e.g. tabanno, à la tabix — before merging this new tool :smile: but in lieu of that this restores the obvious alphabetical ordering of bgzip/htsfile/tabix et al.

[daviesrob]

Thanks, these all look good.