The noundef attribute generally applies to all scalar function
arguments and return values. In the interest of having Clang's
test suite reflect its codegen, it has been updated to include
the new attribute.
Most tests were updated programatically, although some
required more manual intervention, usually due to regexps or
other complications in parsing. Some tests were too burdensome
to update immediately, and to these were applied a cc1 flag to
mask emitting noundef attributes in argument position.