Rationale: cgal_create_CMakeLists and related scripts used to not
consider files ending on anything else than .cpp or .C as C++ sources.
This patch allows for the list of extensions considered as C++ source
files as stated in the g++ man page.
Taucs, Lapack and Blas supports are no longer tested
Approved by the Release Manager
Tested in CGAL-4.5-Ic-97
Conflicts:
Polyhedron/demo/Polyhedron/CMakeLists.txt
removed almost all occurenced (missing UseFiles). While
doing so, some CMakeLists.txt could also be simplified. In fact
many more CMakeLists.txt can be simplified, in one of two ways:
1) add external libs to CGAL_3RD_PARTY_LIBRARIES and
2) call cgal_create_single_source_program