otherwise, implicit transitive linking will pull in the installed
libs, not the ones from the source tree, and the build can fail when
any of the libs' APIs changes.
Also remove some useless #includes.
Hopefully it works, since that's untested (I have no MacOS access). This
is mostly code from file-darktable.c, made generic and factorized into
file-raw-utils.[ch]. At least it still builds and work fine on Linux.
I used the CFBundleIdentifier from `tools/osx/Info.plist.in` in
RawTherapee code. I didn't add a Win32 registry key base though, since I
couldn't find any relevant data for this in RawTherapee code.
...with known plugins
Add new plug-in file-raw-placeholder.c that registers itself for
loading all RAW formats from file-raw/file-formats.h, but does nothing
except returning an error message pointing to darktable and
RawTherapee.
When no real RAW loader is installed, this plug-in is selected
automatically as RAW loader, otherwise the first installed RAW loader
is used. Selecting another in prefs still works as before.