Resolve issue #3812.

The 'defaultText' field inside the 'info' array of a ReflectionParameter
instance is matched against a regex that checks if it complies with the
accepted format for labels and constants names.

Then it checks whether or not it is one of the following reserved words:
'NULL', 'false' and 'true'. If it is, then the function returns FALSE.
Otherwise, TRUE.
Add tests for checking the behavior of the isDefaultValueConstant method from the ReflectionParameter class.
Switch tabs for spaces on issue #3160 test file.
Switch tabs for spaces and clean up the check that is done to see
if the token is a string.