Remove remaining sprintf() uses, and deprecate proj_rtodms() by newly added proj_rtodms2()

[rouault]

Fixes #3423

[seanm]

github didn't notify me about this PR until just now, when you closed it, so I'm only reviewing the code now, but I think there is a mistake. You did not account for the pointer arithmetic on ss that I mentioned in #3423.

char *ss = s;
...
if (!pos) { *ss++ = '-'; sign = 0; }

After this point, s and ss are not always pointing to the same place.

Then you do:

snprintf(ss,sizeof_s,...

What you need is a sizeof_ss that starts the same as sizeof_s but gets decremented when ss gets incremented.

Otherwise you have a buffer overflow. If I'm not mistaken...

[rouault]

You did not account for the pointer arithmetic on ss that I mentioned in #3423.

doh! thanks for the review. Should hopefully be fixed with #3441