Fix forgotten s/razip/bgzip/

Since 9ec7860705a613c659992c437379a2f1374c71ac, fai_build() can read
BGZF-compressed files but no longer RAZF-compressed files.
Remove RAZF source code

Samtools no longer uses RAZF files, and the code has been unmaintained
in htslib so it is not really useful to have it here.  RAZF source code
remains available in older samtools releases and on the samtools
repository's `standalone` branch.

(This answers #74 regarding razf.o being omitted from $(LIBHTS_OBJS),
whence it was incidentally removed by 65617469ffb8e790280448d2d8d61a984135e39b.)
Check CIGAR string has fewer than 2^16 operators

This limit may be raised in the BAM format and htslib in the future,
but for now ensure there is a relevant message when you exceed the
current limit.  Fixes issue samtools/samtools#39 for htslib-based code.
Add a comment to deobfuscate bam_cigar_type

(Closes #96 by cherry-picking ba16f86.)
Fix "unrecognized CIGAR operator" diagnostic

Initialise the rest of the table to -1, not 0 ("M").