Fixed: Failed to locate map data from Memento Mori add-on for Doom

In the Mac Hexen demo some lump names have extra values or'd into
the lump names stored in the lump directory. The WAD file loader
will remove these values when reading the lump directory.

Many of the lump names in Memento Mori's MM.wad similarly have extra
values which appear after the last character in the name.

When translating the lump names ensure that we stop when the name
ends rather than always process all eight characters.

doomsday/engine/portable/src/wadfile.c

@@ -106,7 +106,7 @@ static void WadFile_ReadLumpDirectory(WadFile* wad)
     size_t lumpDirSize;
     ddstring_t absPath;
     const char* ext;
-    int i, j;
+    int i, j, nameLen;
     assert(wad);
 
     if(wad->lumpRecordsCount <= 0) return;
@@ -138,8 +138,12 @@ static void WadFile_ReadLumpDirectory(WadFile* wad)
         F_InitLumpInfo(&record->info);
         record->info.lumpIdx = i;
 
+        nameLen = 0;
+        while(nameLen < LUMPNAME_T_LASTINDEX && src->name[nameLen])
+        { nameLen++; }
+
         Str_Clear(&absPath);
-        for(j = 0; j < LUMPNAME_T_LASTINDEX; ++j)
+        for(j = 0; j < nameLen; ++j)
         {
             /// The Hexen demo on Mac uses the 0x80 on some lumps, maybe has significance?
             /// @todo Ensure that this doesn't break other IWADs. The 0x80-0xff