Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/
The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch up to that fact and revert to their recommended match of BSD-2-Clause. Discussed with: pfg MFC After: 3 days Sponsored by: Netflix
In order to prevent confusion about copyright, rewrite from scratch yyerror.h. See discussion on r335270 for details.
Tested with amd64, arm64, i386, mips