cmake warnings

[sphinxc0re]

I get several warnings from cmake:

including polarssl
CMake Warning (dev) at lib/libevent/cmake/CheckPrototypeDefinition.cmake:29 (if):
Policy CMP0054 is not set: Only interpret if() arguments as variables or
keywords when unquoted. Run "cmake --help-policy CMP0054" for policy
details. Use the cmake_policy command to set the policy and suppress this
warning.

Quoted variables like "EVENT__HAVE_GETHOSTBYNAME_R_3_ARG" will no longer be
dereferenced when the policy is set to NEW. Since the policy is not set
the OLD behavior will be used.
Call Stack (most recent call first):
lib/libevent/CMakeLists.txt:275 (CHECK_PROTOTYPE_DEFINITION)
This warning is for project developers. Use -Wno-dev to suppress it.

CMake Warning (dev) at lib/libevent/cmake/CheckFunctionExistsEx.cmake:31 (IF):
Policy CMP0054 is not set: Only interpret if() arguments as variables or
keywords when unquoted. Run "cmake --help-policy CMP0054" for policy
details. Use the cmake_policy command to set the policy and suppress this
warning.

Quoted variables like "EVENT__HAVE_EPOLL" will no longer be dereferenced
when the policy is set to NEW. Since the policy is not set the OLD
behavior will be used.
Call Stack (most recent call first):
lib/libevent/CMakeLists.txt:221 (CHECK_FUNCTION_EXISTS_EX)
This warning is for project developers. Use -Wno-dev to suppress it.

The problem might be that our cmakelists are a little bit outdated.