cmake: Upgrade to 3.8.2

cmake: Upgrade to 3.8.2

There was a set of changes, those are:

 - CMake now requires librhash for build and as there is no other
   users in OE-Core we make it use its internal copy instead;

 - Copyright.txt checksum has change due new contrubutors and 2017
   year additions;

 - Patch avoid-gcc-warnings-with-Wstrict-prototypes.patch was removed
   as it is not need anymore;

 - Patch 0001-KWIML-tests-Remove-format-security-from-flags.patch was
   removed as it is included in this release.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>