Start work on supporting Android Content URIs in the FileUtil API.

Add tentative Android Content URI support to much of FileUtil.h.

Buildfix

Fix some issues with the file browser in storage URIs.

UI/NativeApp.cpp

@@ -493,7 +493,7 @@ void NativeInit(int argc, const char *argv[], const char *savegame_dir, const ch
 	g_Config.defaultCurrentDirectory = Path("/");
 	g_Config.internalDataDirectory = Path(savegame_dir);
 
-#if defined(__ANDROID__)
+#if PPSSPP_PLATFORM(ANDROID)
 
 	// TODO: This needs to change in Android 12.
 	//
@@ -515,6 +515,8 @@ void NativeInit(int argc, const char *argv[], const char *savegame_dir, const ch
 		} else {
 			ERROR_LOG(SYSTEM, "Couldn't read directory '%s' specified by memstick_dir.txt.", memstickDir.c_str());
 		}
+	} else {
+		INFO_LOG(SYSTEM, "No memstick directory file found. Using '%s'", memstickDirFile.c_str());
 	}
 
 #elif PPSSPP_PLATFORM(IOS)