callback - Remove problematic callback overloads

[geky]

Note: This has no api changes, just removes an erronous set of overloads:

class Func {
public:
    operator()() {};
}

ticker.attach(Func());            // perfectly fine
ticker.attach(callback(Func());   // compile error

Unfortunately, it is very difficult to infer the parameters of function-objects generically in C++03 without any additional type information. The current implementation fails to do so, and the compiler simply bails with "unable to deduce template parameter".

Rather than leaving the user with a small novel of error messages, this patch removes the problematic callback overloads, leaving only callback overloads for the original pointer types.

Also updated the tests based on argument order.

related issue in mbed-events: ARMmbed/mbed-events#24
cc @pan-, @bogdanm, @bridadan

[geky]

/morph test

[mbed-bot]

Result: SUCCESS

Your command has finished executing! Here's what you wrote!

/morph test

Output

mbed Build Number: 1008

All builds and test passed!

[geky]

LGTM?

[bridadan]

I'll admit the C++ craziness is a bit beyond my understanding, but as a sanity check the changes look ok to me. No missing syntax or extra stuff hanging around that shouldn't be there 👍