Document __FreeBSD_version valuse 1100050 and 1100051.


git-svn-id: svn+ssh://svn.freebsd.org/doc/head@46121 c2e8774f-c49f-e111-b436-862b2bbc8956
Fix actual __FreeBSD_version 1100051


git-svn-id: svn+ssh://svn.freebsd.org/doc/head@46122 c2e8774f-c49f-e111-b436-862b2bbc8956