Guard the calls to removed libraw API so that they are not compiled with 0.19. This patch is intended for the 18.08 branch, it simply drops the libraw calls but keeps the API intact (so the corresponding libkdcraw functions will just not do anything when using 0.19). Will post a follow-up revision for master that completely removes the API.
Patch based on digikam commit f5bc69c288dda2509dbdfd9c3c54cd82d88c38ef