Fix #305: trap compiler flags failure in configure
Fix #305: trap compiler flags failure in configure

Add a basic compilation test after the Fortran compiler flag selection
in the configure script, to correctly report the issue if the flags
cause a compilation problem. Previously, the script confusingly reported
in this case that the exit and stop function did not exist.
marenaud/EGSnrc,MartinMartinov/EGSnrc,marenaud/EGSnrc,ftessier/EGSnrc,mchamberland/EGSnrc,ftessier/EGSnrc,nrc-cnrc/EGSnrc,MartinMartinov/EGSnrc,crcrewso/EGSnrc,crcrewso/EGSnrc,mchamberland/EGSnrc,marenaud/EGSnrc,crcrewso/EGSnrc,mchamberland/EGSnrc,marenaud/EGSnrc,MartinMartinov/EGSnrc,mchamberland/EGSnrc,MartinMartinov/EGSnrc,ftessier/EGSnrc,crcrewso/EGSnrc,nrc-cnrc/EGSnrc,marenaud/EGSnrc,marenaud/EGSnrc,crcrewso/EGSnrc,nrc-cnrc/EGSnrc,mchamberland/EGSnrc,nrc-cnrc/EGSnrc,nrc-cnrc/EGSnrc,ftessier/EGSnrc,ftessier/EGSnrc,mchamberland/EGSnrc,MartinMartinov/EGSnrc,ftessier/EGSnrc