Main/cbinding: Add new helper functions to clear out strings (useful if they contain sensitive data). While doing this, added code to the glue init which checks if the version of the structure is compatible with what the client expects. This exposed annoying code duplication between the non-Windows/Windows implementations which is now eliminated.

Main/VBoxCAPIGlue.c: fixed path on OSX

Main/cbinding: remove development leftover

Main/cbinding: bring the C binding to a new functionality level, making them handle both COM and XPCOM based platforms, plus some xsl cleanup to eliminate the $dispatch case which was unused for many years (and will not be used again)