Low: libcrmcommon: Initialize some variables

Cppcheck complained about these. There's no point in spending much
effort on iso8601.c until we start the "replace iso8601.c with GLib"
project, but this is easy enough.

Also avoid a variable-length array and fix a harmless off-by-one (we
don't need max + 1 for array size).

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>