Remove OSMIUM_NORETURN macro

It hasn't been used for a while now.

Author: joto

include/osmium/util/compatibility.hpp

@@ -33,15 +33,6 @@ DEALINGS IN THE SOFTWARE.
 
 */
 
-// Workarounds for MSVC which doesn't support [[noreturn]]
-// This is not needed any more, but kept here for the time being, because
-// older versions of osmium-tool need it.
-#ifdef _MSC_VER
-# define OSMIUM_NORETURN __declspec(noreturn)
-#else
-# define OSMIUM_NORETURN [[noreturn]]
-#endif
-
 // [[deprecated]] is only available in C++14, use this for the time being
 #ifdef __GNUC__
 # define OSMIUM_DEPRECATED __attribute__((deprecated))