Compile .ino / .pde files directly to improve error messages

Before, they were copied to a .cpp file to add the Arduino.h/WProgram.h
include. However, this would cause the compiler error messages to not
refer to the right file and line numbers, making it hard to use the
compiler output in an editor like vim to point out errors.

By using gcc's -include option, there is no need to modify the ino/pde
file before compiling. However, we will need to explicitely tell gcc
that the source file is c++, because of the non-standard extensions.