Interpret TTY_NR column on Linux,

translate dev_t to major:minor on other platforms.
Closes #316.

OpenFilesScreen.c

@@ -102,7 +102,6 @@ static OpenFiles_ProcessData* OpenFilesScreen_getProcessData(pid_t pid) {
          fdata = nextFile;
          item = &(fdata->data);
       }
-      assert(cmd >= 0 && cmd <= 0xff);
       item->data[cmd] = xStrdup(line + 1);
       free(line);
    }