The HDN_ITEMCHANGING notify should have the new data instead of the
old one.  Both HDN_ITEMCHANGING and HDN_ITEMCHANGED now have the text
field if it changed.

Based on some documentation by Rob Shearman.

- Find menus by ID: Proper fallback to popup menus.
- Use the menu ID, not the handle for the fallback.
- Save the fallback menu's position.

Based on a patch by Rob Shearman.

Also print a warning if HAL support is not compiled in.

buffer for interfaces and the buffer actually used.