ENH: Added cmStringStream class to wrap std::stringstream or std::strstream depending on the platform.  The interface is that of std::stringstream, so no "ends" or "rdbuf()->freeze(0)" lines are needed.

ENH: Re-ran autoconf to include changes to corresponding configure input.  This adds a test for the availability of sstream.

ENH: Added test for sstream header.  Defines CMAKE_NO_ANSI_STRING_STREAM if the header doesn't exist.

ENH: define OPENGL_LIBRARY_PATH (path to OPENGL_LIBRARY) so that it can be used to search for other OpenGL-related libs

ENH: FindLibrary can now use the makefile to add some compiler-specific lib search path (depending on the generator).