Drop functions and API that depend on removed libraw features. The soversion was intended to be set to '30.0.0', quite an unusual value. This didn't work due to a typo, so in practice the soversion was 5 (the major lib version). Bump it to 6 to account for the removed API.
Patch based on digikam commit f5bc69c288dda2509dbdfd9c3c54cd82d88c38ef