C++11 and attach interrupts using lambdas

I wanted to support multiple instances of a class in a library which uses attachInterrupt

I can now do:
    auto mylambda = [&]() {this->touchSense();} ;
    attachInterrupt(m_sensorPin, mylambda , RISING);

Standard function pointers still work.

I needed some cleanups to allow the entire library to build using gnu++11 and some minimal tidy up to allow <functional> to be #included.