bc.c

Now, passing a keyword argument that is not expected will correctly report
that fact.  If normal or detailed error messages are enabled then the name
of the unexpected argument will be reported.

This patch decreases the code size of bare-arm and stmhal by 12 bytes, and
cc3200 by 8 bytes.  Other ports (minimal, unix, esp8266) remain the same in
code size.  For terse error message configuration this is because the new
message is shorter than the old one.  For normal (and detailed) error
message configuration this is because the new error message already exists
in py/objnamedtuple.c so there's no extra space in ROM needed for the
string.