config: stop nesting config files so deep

It is possible to call SDL_GetPrefPath with nullptr as first
argument. This reduces the path from `$XDG_DATA_HOME/Outrage
Entertainment/Descent 3` to just `$XDG_DATA_HOME/descent3`. This
follows similar spirit to what e.g. Unreal Tournament did (going from
`~/.loki/ut` to just `~/.utpg` once it was no longer maintained by
Loki Software).

Author: jengelh

Descent3/init.cpp

@@ -1418,7 +1418,7 @@ void InitIOSystems(bool editor) {
    */
 
   // Writable preference path
-  std::filesystem::path pref_path = ddio_GetPrefPath(D3_PREF_ORG, D3_PREF_APP);
+  std::filesystem::path pref_path = ddio_GetPrefPath(nullptr, D3_PREF_APP);
   if (pref_path.empty()) {
     Error("Failed to get preference path!");
   }

lib/d3_platform_path.h.in

@@ -21,8 +21,5 @@
 // Platform-specific compile-time defined location of data files
 #define D3_DATADIR "@D3_DATADIR@"
 
-// Part of preference path (organization)
-#define D3_PREF_ORG "Outrage Entertainment"
-
 // Part of preference path (application)
-#define D3_PREF_APP "Descent 3"
+#define D3_PREF_APP "descent3"

linux/lnxdata.cpp

@@ -70,7 +70,7 @@ oeLnxAppDatabase::oeLnxAppDatabase() {
   // Open up the database file, for reading, read in all data and keep it in memory
   // then close the database
 
-  std::filesystem::path prefPath = ddio_GetPrefPath(D3_PREF_ORG, D3_PREF_APP);
+  std::filesystem::path prefPath = ddio_GetPrefPath(nullptr, D3_PREF_APP);
   if (prefPath.empty()) {
     LOG_FATAL << "Couldn't find preference directory!";
     exit(43);