Updated the following:
* poky.ent to use new variables values for 2.6.1
* mega-manual.sed to use "2.6.1" string for links
* *.xml manual files to have a new entry in the manual history
tables. Using the variable for the most recent entry.
Hard-coded "November 2018" for the previous release, which
was "2.6".
(From yocto-docs rev: bada424e14169d1ae378c0481970e55ce8f5df51)
Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>