PHP: Improve some comments
Cleanup: Rename colonpos var to enddelpos

It is makes more sense that the position of enddel is called enddelpos and
not colonpos, specially because the end delimiter is not always a colon.
PHP: Fall back to default dialect in PHP parsing after adding new units

Before this, when a PHP simple variable syntax entry was found after any
entry using the define syntax, that entry was not detected.
PEP8: W291 trailing whitespace