Bump the minimum version of CMake to 3.5, to be able to compile with CMake 4.0

[jmcarcell]

BEGINRELEASENOTES

• Bump the minimum version of CMake to 3.5, to be able to compile with CMake 4.0
• Don't set CMP0005 to OLD since it has to be set to NEW with CMake 4.0 and onwards. Escape
  the DLCCD_DB_INIT_DEFAULT definition accordingly

ENDRELEASENOTES

See https://cmake.org/cmake/help/latest/release/4.0.html#deprecated-and-removed-features

Here I'm not sure what's best. I added the following:

get_directory_property(COMPILE_DEFINITIONS COMPILE_DEFINITIONS)
message(WARNING "Current definitions: ${COMPILE_DEFINITIONS}")

after DLCCD_DB_INIT_DEFAULT is set and I get an empty string in the current version, while with this PR it will become

Current definitions:
LCCD_DB_INIT_DEFAULT="localhost:lccd_test:calvin:hobbes"

I see this is only used in https://github.com/iLCSoft/LCCD/blob/master/source/src/lccd.cc#L44. One possibility would be to remove the definition and just return an empty string, which is the current behaviour.