- Remove unnecessary casts from malloc() & memcpy() calls
- rgb.c: fix -Wdiscarded-qualifiers warning
- rgb.c: if filename is too long, report error instead of truncating
- README: provide more information on --with-rgb-db-type
- configure: Add --with-rgb-db-library option
- gitlab CI: build all 3 --with-rgb-db-type=(text|dbm|ndbm) options