Disable MSVC warning 4098

a.k.a. "'void' function returning a value", caused by returning a void in a
function that returns void. Such as:

void foo() { }
void bar()
{
    return foo();
}

Which can happen due to some generalized macros that generate wrappers.

CMakeLists.txt

@@ -172,6 +172,7 @@ IF(MSVC)
     SET(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -D_DEBUG")
     ADD_DEFINITIONS(-D_CRT_SECURE_NO_WARNINGS)
     ADD_DEFINITIONS(-D_CRT_NONSTDC_NO_DEPRECATE)
+    ADD_DEFINITIONS("/wd4098")
 
     IF(NOT DXSDK_DIR)
         STRING(REGEX REPLACE "\\\\" "/" DXSDK_DIR "$ENV{DXSDK_DIR}")