Flags controlling link/append code are split between two enums, one in
`DNA_space_types.h` and one in `BLO_readfile.h`.
This commit:
- Moves flags exclusively used in WM and BLO code to `eBLOLibLinkFlags`
in `BLO_readfile.h`. Flags in `eFileSel_Params_Flag` from
`DNA_space_types.h` are now only the ones effectively used by the
file browser editor code too.
- Fixes some internal utils in `readfile.c` still taking `short` flag
parameter instead of proper `int` one.
NOTE: there are a few other flags that could probably be moved to
`eBLOLibLinkFlags` (at the very least `FILE_LINK`, probably also
`FILE_AUTOSELECT` and `FILE_ACTIVE_COLLECTION`), since those are not
effectively used by the file browser, and control linking/appending
behavior, not filebrowser behavior.
However for now think it's safer to not touch that.
3042994c91