This fixes Mantis bug #545.
compiler/parse_tree_out.m:
Put brackets around functor names in "where direct_arg is" attributes.
compiler/mercury_to_mercury.m:
Provide a function for doing that.
tests/valid_seq/xml_event_read.m:
tests/valid_seq/xml_event_read_helper.m:
A slightly modified version of the Mantis test case.
tests/valid_seq/Mmakefile:
tests/valid_seq/Mercury.options:
Enable the new test case, and compile it with intermodule optimization
to (try to) tickle the bug.
