Add support for switch statements/unary ops for GCC feature extractor.

    * gcc_plguin/feature-extract.cpp (mageec_featextract_exec): Add
    feature extractor support for counting switch statements and
    unary ops.
Change GCC plugin output to only print decision if override occurs.

	* gcc_plugin/gcc-callbacks.cpp (mageec_pass_gate): Add flag to
	only print out MAGEEC's decision if it overrides the compiler.