Duke3D: Loading savegames fails to load maphack files defined through mapinfo

Thanks to Francesco Vindigni for bringing this problem to my attention.

As of r9476, if a maphack is defined through the use of the mapinfo DEF command, and assuming this file has a path and filename that differs from that of the corresponding map, then loading a savegame of that map will fail to load the maphack file. This occurs because, similarly to per-map art, the savegame currently always assumes the maphack file to have the same path and filename (minus extension) as the map it is applied to. This assumption is violated by the mapinfo command, using which the mhk file may be placed in any subfolder, under any filename.

In particular, this problem affects the HRP and the Duke 3D Voxel Pack.

To reproduce, download the following zip file and activate Polymer to see the dynamic lights: maphack_bug.zip

Before save load, maphack lights are present:

After save load, maphack lights are gone: