Add Automake compile function instead of its symbolic link

       * compile: Add compile file, replacing symblink.
Add feature vector printing support into common code.

This printer supports the previous textual output as well as outputting the
feature vector as JSON, allowing the vector to be easily parsed by external
tools.

	* gcc_plugin/feature-extact.cpp (mageec_featextract_exec): Don't
	print out feature vector manually, use new printing interface.
	* include/mageec/mageec-features.h (mageec_feature): Add description
	member, with getter and constructor to use the new member.
	* mageec/features.cpp (pad_string): Add static string pad function.
	(mageec_feature::dump_vector): Add plain text/JSON feature vector
	printer.
	(mageec_feature::mageec_feature): Add constructor which utilizes
	new description member.