Fix filtering of INI directives to respect leading whitespaces

[madmajestro]

Directives are now correctly filtered out if the line in the php.ini file begins with whitespace characters.

[madmajestro]

While analyzing the issue krakjoe/apcu#578 I noticed that the tmp-php.ini file generated by make test can unexpectedly contain extension directives that should have been filtered out, causing all tests to fail.

This happens, if the php.ini file used as basis contains extension directives with leading spaces. In this case, these directives are not filtered out. This will cause all tests to fail if these extensions cannot be loaded during the test run.

[madmajestro]

I picked the wrong branch by mistake. Target branch is 8.3 now.

[iluuu1994]

Thank you @madmajestro!