starting to implement 'default.args'

Basic implementation is okay, but calls with dots
not working
cleaned-up error msg
'default.args' mostly working with dots now

But we seem to be getting the same argument twice in some
cases so clearly something is not 100% right
'default.args' working
starting to address PROTECT issues, but not solved
addressing protection issues
adding tests for use with valgrind
adding NEWS and version bump
Merging dev: enables 'default.args' option