profiling: fix profile_cmp impl and docs

The order seems strange, though it's the way it is in vanilla vim.
profiling: simplify profile_passed_limit

Trying to be too clever to avoid overflows provides equivalent behaviour to
the new code, as far as I can see.
profiling: add profile.{c,h} to clint and -Wconv

Fix 2 issues clint reported:
- don't use sprintf, use snprintf
- don't use long, use int16_t/int32_t/...
profiling: fix typo, remove useless comment