Adding `strcmp_i` function to `parsing`.

Adding function `strcmp_i` for comparing strings while ignoring
case to `parsing`.c/h.

Adding associated tests of this function to `check_parsing.c`.
Adding `strip` function to `parsing`.

Adding `strip` function for stripping end-of-line characters and leading
and trailing whitespace from a character array.

Adding associated tests of new function to `check_parsing.c`.
Updating `strip` function.

The function was duplicating the input string in memory to remove the
end-of-line character if present. Updating function to simply decrement
the length of the string if it sees an end-of-line character, which
avoids duplicating the string.