Automatically detect global variable types

[cedric-anne]

Instead of forcing developers to add PHPDoc for all global variables, we can resolve their type automatically.

The resolution is based on the variable name and the risk that a plugin declares a variable with the same name that a global variable of GLPI exists, but, in this case, it is still possible to enforce the type with a dedicated PHPDoc block (see the tests/data/GlobalTypeResolver/global-statement-with-phpdoc.php test file).

This will permit, for instance, in a future GLPI version, to change the type the $CFG_GLPI or the $PLUGIN_HOOKS variables if we decide to replace it by dedicated objects that implements the ArrayAccess interface.