- 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

Apply still relevant local changes.

r124183: Work around a `label defined but not used' warning.
r179549: De-register declarations.
r179657: De-register declarations in non-dot-c files.
r181269: Mark yy_fatal_error() as __dead2.
r228992: Spelling fixes.
r240518: Correct double "the the".

Add flex 2.5.37 from flex.sourceforge.net to contrib.

Disable keyword expansion.

Clean up svn:keywords property.

import vanilla flex version 2.5.35

Reviewed by: cognet
Approved by: cognet