Add -fno-backtrace for gfortran 4.8.0 and above

[andreww]

Report of errors from make check with gfortran 4.8.0... Part of my reply to Francisco: I think the errors you see when doing "make check" with gfortran 4.8.0 are because new gfortrans will build executables such that they dump a backtrace if they abort (this had to be enabled with a command line switch for earlier versions). FoX will trigger an abort by default in response to things like trying to write a malformed XML document and this is tested in the test suite. The presence of a backtrace is confusing the test harness. You can work around this by adding -fno-backtrace to the FFLAGS line in arch.make after running configure and before running make or make check. We should probably make the configure script test for the presence of a backtrace in this case and turn it off (by adding the flag). That's a non-trivial little project in itself though.

[andreww]

Fix (for travisCI) via d2ad441

Need to add a note to the documentation about this too.

[andreww]

There is also the GFORTRAN_ERROR_BACKTRACE. environment variable. Probably a better fix the the CI.