Switch on gcc47 and switch off gcc41

Switch on gcc47 and switch off gcc41

Replace GCC 4.1 with GCC 4.7.  The primary compiler remains GCC 4.4
and the source and makefiles for GCC 4.1 remain intact so it can be
brought back if necessary.  All references to GCC 4.1 in documentation
where updated to reflect version 4.7.

A full world build is probably required after this point.