Re-add CMake Port Group to fix it breaking other ports depending on it.
Fix CMake PortGroup, which modification due to ticket #40648 broke other ports.

Unfortunately, the CMake man pages and
<http://www.cmake.org/cmake/help/v2.8.12/cmake.html> do not mention at
all that the environment variables CFLAGS, CXXFLAGS, and LDFLAGS get
honored by CMake upon its first call in a new build directory. The
book "Mastering CMake" (4th edition) by Ken Martin and Bill Hoffmann
mentions it only briefly in Section 2.7 "Specifying the Compiler to
CMake" and the end of Appendix A.

Therefore, the previously proposed modification of the CMake PortGroup
to honor configure.optflags and configure.cppflags proposed in
MacPorts ticket #40648 can be simplified as other language-specific
flags were already forwarded correctly to CMake via the above
environment variables.

This should also fix the observed compilation problems of other ports
using CMake to configure their sources for the build phase.