Write PhpFileCheck and PhpFileCheckVisitor classes for easier checking of PHP files
Create FunctionCallCheckVisitor
Base VIPRestrictedCommandsCheck on PhpFileCheckVisitor
In BaseScanner, invoke PHP analyzing from scan() so it isn't done twice
Temporarily comment out eval check
Migrate ForbiddenFunctionsCheck to FunctionCallCheckVisitor
Create PhpFileCheckTestBase to faciliate testing of PHP file checks
Add ForbiddenFunctionsTest