[All] Fixed multiple issues during build on Linux

- Added some fixes introduced by RodoMa92 in PR198

- Lack of AVX2 extension (should be done differently in the future)
- Disable deprecated-volatile warning
- Added missing override in posix EventInfo, ImGui notification class and XContent class
- Removed not used XAudio2.h include in XMP
- Fixed missing switch-case in XObject
- Added fugly template in native_list.h
- Fixed multiple smaller issues

src/xenia/kernel/xsocket.h

@@ -108,7 +108,7 @@ class XSocket : public XObject {
   X_STATUS Close();
 
   X_STATUS GetOption(uint32_t level, uint32_t optname, void* optval_ptr,
-                     int* optlen);
+                     uint32_t* optlen);
   X_STATUS SetOption(uint32_t level, uint32_t optname, void* optval_ptr,
                      uint32_t optlen);
   X_STATUS IOControl(uint32_t cmd, uint8_t* arg_ptr);