CMake: avoid /W3 overriding warnings and enable -DUNICODE on Windows.

Consistent with how all other Magnum projects do it.

src/CMakeLists.txt

@@ -23,6 +23,17 @@
 #   DEALINGS IN THE SOFTWARE.
 #
 
+# On MSVC remove /W3, as we are replacing it with /W4
+if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC" OR CMAKE_CXX_SIMULATE_ID STREQUAL "MSVC")
+    string(REPLACE "/W3" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+endif()
+
+# On Windows enable UNICODE/_UNICODE macros to avoid accidentally passing UTF-8
+# values to ANSI functions
+if(CORRADE_TARGET_WINDOWS)
+    add_definitions("-DUNICODE" "-D_UNICODE")
+endif()
+
 set_directory_properties(PROPERTIES CORRADE_USE_PEDANTIC_FLAGS ON)
 
 add_subdirectory(Corrade)