Archives: Implemented ExtSaveData and SharedExtSaveData

They will be stored in /extsavedata/SDMC and /extsavedata/NAND respectively.
Also redirect some APT_A functions to their APT_U equivalents.
Implemented the gamecoin.dat file in SharedExtSaveData in the PTM module.
Implemented formatting the savegame.
Retake a previous savegame if it exists instead of reporting them as not formatted every time a game is loaded.

src/core/file_sys/archive_extsavedata.cpp

@@ -0,0 +1,59 @@
+// Copyright 2014 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <sys/stat.h>
+
+#include "common/common_types.h"
+#include "common/file_util.h"
+
+#include "core/file_sys/archive_extsavedata.h"
+#include "core/file_sys/disk_archive.h"
+#include "core/settings.h"
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// FileSys namespace
+
+namespace FileSys {
+
+static std::string GetExtSaveDataPath(const std::string& mount_point, const Path& path) {
+    std::vector<u8> vec_data = path.AsBinary();
+    const u32* data = reinterpret_cast<const u32*>(vec_data.data());
+    u32 media_type = data[0];
+    u32 save_low = data[1];
+    u32 save_high = data[2];
+    return Common::StringFromFormat("%s%s/%08X/%08X/", mount_point.c_str(), media_type == 0 ? "nand" : "sdmc", save_high, save_low);
+}
+
+Archive_ExtSaveData::Archive_ExtSaveData(const std::string& mount_point)
+        : DiskArchive(mount_point), concrete_mount_point(mount_point) {
+    LOG_INFO(Service_FS, "Directory %s set as base for ExtSaveData.", this->mount_point.c_str());
+}
+
+bool Archive_ExtSaveData::Initialize() {
+    if (!FileUtil::CreateFullPath(mount_point)) {
+        LOG_ERROR(Service_FS, "Unable to create ExtSaveData base path.");
+        return false;
+    }
+
+    return true;
+}
+
+ResultCode Archive_ExtSaveData::Open(const Path& path) {
+    std::string fullpath = GetExtSaveDataPath(mount_point, path);
+    if (!FileUtil::Exists(fullpath)) {
+        // TODO(Subv): Check error code, this one is probably wrong
+        return ResultCode(ErrorDescription::FS_NotFormatted, ErrorModule::FS,
+            ErrorSummary::InvalidState, ErrorLevel::Status);
+    }
+    concrete_mount_point = fullpath;
+    return RESULT_SUCCESS;
+}
+
+ResultCode Archive_ExtSaveData::Format(const Path& path) const {
+    std::string fullpath = GetExtSaveDataPath(mount_point, path);
+    FileUtil::CreateFullPath(fullpath);
+    return RESULT_SUCCESS;
+}
+
+} // namespace FileSys