#1 Implement modules support and import() function

<?php
    var_dump(import('dummy')); // true, module loaded
    var_dump(import('dummy2')); // false - no such module
    var_dump(import('dummy')); // true - module already loaded
?>

In scope of this ticket, we need to implement a module system for P# Interpreter. It is a necessary step in order to divide the existing code into separate, dynamically loadable modules. This includes import() function, that can be called from inside a script. It should return a boolean value (false on any error, or true otherwise). What is more, some 'dummy' module has to be written for tests. Requirements are: * import() has to check if library is already loaded, * import() should return true on successful library load, or if the module has been already loaded - false otherwise, * import() should take a module name as parameter, then add extension automatically and look for it in some predefined directory * all loaded modules should be kept in some structure (linked list or better a hash map); some mechanisms are already implemented in PH7 Engine, * structure saved in "ph7_vm" has to contain information about: module name, module version, short module description * all these information should be returned by some init() function implemented in module and called from builtin_import() * module should register all its constants and functions * all libraries have to be unloaded on program exit, to free up memory * multiplatform (Unix .so & Windows .dll) support Some code snippet: <?php var_dump(import('dummy')); // true, module loaded var_dump(import('dummy2')); // false - no such module var_dump(import('dummy')); // true - module already loaded ?>