New release notes: Thread supports under Linux emulation on alpha,

New release notes:  Thread supports under Linux emulation on alpha,
an(4)/ancontrol(8) WEP, ng_one2many(4), softupdates bugfixes/
enhancements, OpenSSH agent/X forwarding bug fixed, ssh(1) no longer
SUID root, OpenSSL->0.9.6, binutils->2.10.1, lastlogin(1),
newfs(1) write combining (+MFC), config(8) buffer overflows fixed,
pcm(4) drivers compiled into GENERIC by default.

Other MFCs:  Write combining for crash dumps.

Delete a duplicated note on mergemaster(8).