Hook up IPSEPCOLA into GNU build process.

Hook up IPSEPCOLA into GNU build process.
To enable use "./configure --with-ipsepcola"

Changes include minor C++ source changes to work with latest gcc
	csolve_VPSC.cpp  - add "#include <cassert>"
	constraint.h - remove classname prefix in declaration of slack()
	variable.h - remove classname prefix in declaration of position()