Split parameter and tag storage in annotationparser parse tree

Split parameter and tag storage in annotationparser parse tree

This avoids tags overwriting parameters if they happen to
share the same name. For example, this was triggered by
valid code in libgnome-keyring.

tests/scanner/regress.c and tests/scanner/regress.h test
written by Colin Walters <walters@verbum.org>.

https://bugzilla.gnome.org/show_bug.cgi?id=672254