Include parser-defs.h in cp-name-parser.y

This changes cp-name-parser.y to include parser-defs.h, removing the
copy-pasted declaration of parser_fprintf.  This can be done now that
cp-name-parser.y does not define any global variables.

gdb/ChangeLog
2018-06-01  Tom Tromey  <tom@tromey.com>

	* cp-name-parser.y: Include parser-defs.h.
	(parser_fprintf): Remove declaration.