Convert warnings to errors on CI, or they'll go unnoticed.

Calculation can take very long. Most Unix-ish OSes have utilities to do this.

It was troubling me. Mimicking 'gg' would have been hacky and would need
additional processing... 'g' was free. Who cares even if you press twice? ;)

Test on Travis

This is consistent with the fact that custom LDFLAGS are already allowed, and
for once, it makes warning options easier to control.

Also use automatic variables $@ and $^ consistently.

Remove dependency on cut.

This commit adds dependencies on file, openssl and cut binaries.

We closely follow the output for stat(1).

1. Have a faster copy of strlcpy()
2. Remove redundant legacy files
3. Fix an issue with NULL check on array name

Numeric is numeric i.e., n, -n. +n.
Other forms such as --n, ++n, -c, +c should not be considered numeric.

If size is same (e.g. dirs), use alphanum sort.

Add .gitignore to ignore compilation products