tests/submodules/*.m:
Rename modules as mentioned above.
Indent nested submodules to make them stand out.
Group foreign_procs by what predicate they implement, not by
their implementation language.
tests/submodules/*.m:
tests/submodules/*.err_exp:
tests/submodules/Mmakefile:
tests/submodules/Mercury.options:
Update all references to the moved modules.
