Add support for a system to select custom manglers

[chuggafan]

This is something we should support for future reference to allow OrangeC compiled C++ to work with MSVC or GCC compiled code for either Linux or Windows, if we can create a system with custom select manglers I think overall we'd have a better position overall for interoperability with outside programs and this could be useful to coordon off mangling as a whole into a standardized way to set up mangling/demangling.

Of course, we'd also have to be able to identify what mangling type each thing is for stuff like onm but that's a different story...

[LADSoft]

this is loosely related to #252... the only reason I can think of to support multiple manglers is for linux support!