Fixed build break when enabled SRT_ASSERT. Enabled _DEBUG in debug mode

[ethouris]

Changes:

1. INT_MAX replaced with std::numeric_limits<int>::max().
2. Added <limits> header in buffer_rcv.cpp
3. Added -D_DEBUG when ENABLE_DEBUG is on (debug only).
4. Added cast in a condition to clear out the warning

[maxsharabayko]

As discussed offline, MSVC itself defines _DEBUG for a Debug build configuration and NDEBUG for a Release build configuration.
The build configuration is set during the build, not at the CMake's project configuration stage.

(configure)
cmake ./
(build)
cmake . --build --config debug

Running cmake ./ -DCMAKE_BUILD_TYPE=Debug defines _NDEBUG for all build configurations of MSVC. The _NDEBUG is thus defined in the release build as well.

Setting -DCMAKE_BUILD_TYPE for MSVC is probably not the right thing to do. Still, someone can do it, and redefining MSVC standard macros is not a good approach.

[maxsharabayko]

Please address the above comment. 👆

[ethouris]

Ok, so I think we'll put this block that sets up the CMAKE_BUILD_TYPE basing on flags under NOT MICROSOFT condition. The problem here is that this should be blocked for all cases when the build type is not selected for configuration - which is known to be true currently for MSVC. Might be that there are also some other build systems that do it this way, but I'm not sure if cmake has a universal way to recognize it - this will be then a kind of temporary workaround.