CMake: No `LANGUAGES` results in C++ compiler requirement

[d5UtQvp8QQU9]

Building tinydtls with cmake currently requires a working C++ compiler due to the omission of the LANGUAGES specification:

tinydtls/CMakeLists.txt

Line 24 in d9738c3

project(tinydtls)

I do not see why a working C++ compiler should be required to build tinydtls.

By default C and CXX are enabled if no language options are given.
Source: https://cmake.org/cmake/help/latest/command/project.html#options

[boaks]

Thanks for reporting.
I will fix it.

[boaks]

See PR #281