[boost] [graph] PATCH to eliminate gcc 4.2 warnings when compiling boost/graph/read_dimacs.hpp

Attached is a patch that changes the definition of `err_message` in boost/graph/read_dimacs.hpp@66260 from: static char *err_message[] to: static const char *err_message[] This will eliminate the warnings that were recorded at: http://www.boost.org/development/tests/trunk/developer/output/Sandia-gcc-4-2... Daniel