Add documentation how to avoid linker problems if name mangling changes OR work around that altogether

[robb]

Essentially:

• Explain people never to link against Asterism, because that will fail if clang ever changes the name mangling of overloaded C methods

or:

• Move everything over to static inline defined in the .h files

/cc @wrl

[robb]

I begin to like the static inline approach. I feel like Asterism is very bare bones so being a fully transparent set of what would effectively amount to macros could help maintain that focus.

[robb]

@kastiglione iirc you said you used overloaded C functions in production, what's your take on this?

[kastiglione]

I've only used overloaded C functions in application code, where versioning and name mangling wasn't an issue.

For overloaded functions in a library, I would take this approach: http://garbagecollective.quora.com/Overloadable-functions-across-link-unit-boundaries-in-C

It's a little extra work, but seems like a reliable solution.

[robb]

Looks like a great compromise, thanks!