Add error if raylib.h is included in a C++98 program (#3093)

The color macros don't work properly in C++98, because they require
aggregate initialzation, which is a C++11 feature. So, explicitly state
how to fix this issue, instead of letting the compiler give a more vague
error message like:

main.cpp:8:23: error: expected '(' for function-style cast or type construction
      ClearBackground(BLACK);
                      ^~~~~
/opt/homebrew/Cellar/raylib/4.5.0/include/raylib.h:179:35: note: expanded from macro 'BLACK'
 #define BLACK      CLITERAL(Color){ 0, 0, 0, 255 }         // Black

NOTE: Don't use this check with MSVC because by default, it reports
199711L  regardless of any C++ version passed on command line
Only passing `/Zc:__cplusplus` will make MSVC set this correctly

see: https://learn.microsoft.com/en-us/cpp/build/reference/zc-cplusplus

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