Upgrade waf to 1.7.10 and fix included wscripts
This is a massive upgrade removing almost all pre-waf 1.6 script code. In addition, this does away with custom pkgconfig.py script for making .pc files and replaces it with waf's builtin mechanism.
Massive thanks to Alex Afanasyev for ideas and bugfixing, to Alina Quereilhac for bugfixing and testing, and to Tom Henderson for thorough testing.