MFH: r408434

Adjust MASTER_SITES for all digiKam ports.

digiKam 4.2.0 which is currently in ports is quite old, and was moved along
with all releases older than 4.10.0 to another location in download.kde.org.

This should fix `make fetch' for graphics/digikam* and graphics/kipi-plugin*.

Approved by: portmgr blanket approval