Name Mangling

[iwillspeak]

We need to come up with some way of mangling the names of functions to
support modules. Would probably make sense to use the Itanium ABI like
everyone else. Can't find a crate which provides mangling for it
though, just demangling.

This should fix: #25

[iwillspeak]

Thinking we want a simple scheme for mangled names based on the Itanium ABI:

Seen as we don't have overloading and no templates/generics we can get away with just encoding the path. The suggested encoding is therefore the itanium-encoded path, with a _U prefix. e.g.:

foo::then::bar => _U3foo4then3barE