Check that function and task declarations can use a visible type identifier as
the declaration name. Cover both ANSI declarations and the non-ANSI forms where
the name is parsed without a separate return type or port list.
Also check class method declarations where the method name is the same as the
enclosing class name. Add GitHub issue #670 coverage for the `function void`
case using the issue-based regression naming scheme.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>