Making an asynchronous method call and proxying the result as a signal

[Pontus Carlsson]

Basically I need to implement a way to make asynchronous calls into a 
Lua library.
The library itself for the time being is now only capable of connect to 
signals and adding matched signal interception.

Because of Lua's bulky and unsafe threads implementation it seems as the 
most reliable approach is to proxy the method_return into the Lua 
librarys internally registered bus name.
So, my question is simple as stated in the title, and how exactly does 
one make an asynchronous method call using the C API?

I'm also wondering if and how it's possible to retrieve a method 
declaration, i.e. the parameter list etc?