Made c++11 an internal flag so other projects can use c++17

CMakeLists.txt

@@ -34,7 +34,7 @@ target_include_directories(assimp PRIVATE
 )
 
 if(NOT MSVC)
-	target_compile_options(assimp PUBLIC
+        target_compile_options(assimp PRIVATE
 		$<$<COMPILE_LANGUAGE:CXX>:-std=c++11>
 	)
 else()