Switch from strtol to hts_str2uint in mod parsing

[cjw85]

This saves around 10-15% in programs calling the modified base APIs.

[jmarshall]

Looks like a good idea.

If you lift the declarations of tmp (to the char *cp declaration) and of (as, say, failed, to the top) these can stay as one-liners, which would be nice (clearer).

[daviesrob]

I'd agree that lofting particularly of could be useful. It could even be tested at the end to detect overflows, which isn't done at the moment.

It would also be a good idea to change the strtol() calls in bam_parse_basemod2(). bam_mods_at_next_pos and bam_parse_basemod2 rely somewhat on the strings being parsed in the same way, so I'd be a bit worried about subtle differences between strtol() and hts_str2uint() resulting in odd things happening if the input is not strictly spec-compliant.

[jmarshall]

And now there's no need to modify a bunch of surrounding lines by adding { … }.

[cjw85]

Removed.

[cjw85]

@jkbonfield This site made me think for a minute; the interplay of the ternary and the if(!cp_end) worried me. I believe I have the logic correct, it reads a little more direct now as a consequence.