Remove svn:mergeinfo from the releng/10.0 branch.

After branch creation from stable/10, the stable/10 branch mergeinfo
was moved to the root of the branch.

Since there have not been any merges from stable/10 to releng/10.0
yet, we do not need to track any of the existing mergeinfo here.

Merges to releng/10.0 should now be done to the root of the branch.

For future branches during the release cycle, unless otherwise noted,
this change will be done as part of the stable/ and releng/ branch
creation.

Discussed with: peter
Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Update byacc to 20130304

update to version 20120526

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)