Help with making a port C11 compliant

[Walter Schwarzenfeld]

Write in the Makefiles of math/cln and math/GiNaC

USE_GCC=     4.7
(you can also use 4.8 or 5)
and
CXXFLAGS+=      -D_GLIBCXX_USE_C99

I have tested it with 4.7 and 5 in the port and with gcc5 with poudriere 
in a 93amd64 jail (the test with 4.7 is running in the moment).
And it builds fine.