Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Rewrite scan procedure with a FSM. This improves code readability by
making clear transits between different states, and avoids bug with
handling repeated $'s.

Reviewed by: bapt
Differential Revision: https://reviews.freebsd.org/D3221

Replace GNU RCS ident with a BSD license ident

Rationale: ident(1) is useful out of RCS, lot of scripts are using ident(1) and
failing when base is built WITHOUT_RCS.

This version is:
- fully compatible with RCS 5.7 ident.
- fully compatible with RCS 5.9 ident.
- passes all ident test from GNU RCS 5.9 test suite

This version has support for: svn extension for the Keyword id (double colon and
# before last $)

Différences with GNU RCS ident:
- no long options as found in GNU RCS 5.9 (but not commented there).
- '-V' reports nothing but has been added for compatibility.

Differential Revision: https://reviews.freebsd.org/D3200
Reviewed by: pfg