Log Message:
cproto: update to 4.7o.

Provided by Thomas Dickey in private email.

2018/05/25 (4.7o)
- correct logic in CF_YACC_ERROR macro for clang.

2018/05/24 (4.7n)
- add check_errors rule to show error messages from test-cases
- correct logic in YACC_HAS_YYTOKS case for isascii().
- updated/improved test-packages.
- updated configure macros
- update config.guess