Remove most usages of strncmp()

Remove most usages of strncmp()

The supposed safety blanket of this function is better handled by
explicit length checking and usages of strlen() on known NULL-terminated
strings rather than hoping things fit in a buffer. We also have no need
to fully fill a PATH_MAX length variable with NULLs every time as long
as a single terminating byte is there. Remove usages of it by using
strcpy() or memcpy() as appropriate, after doing length checks via
strlen().

Signed-off-by: Dan McGee <dan@archlinux.org>