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

Import byacc from invisible island, it brings us lots of compatibilities with
bison, keeping full compatibility with our previous yacc implementation.

Also bring the ability to create reentrant parser

This fix bin/140309 [1]

PR: bin/140309 [1]
Submitted by: Philippe Pepiot <ksh@philpep.org> [1]
Approved by: des (mentor)
MFC after: 1 month

Import byacc 20120115

Approved by: des (mentor)