vold: rename from "ext4 encryption" to fscrypt

We support file-based encryption on both ext4 and f2fs now, and the
kernel API is the same.  So rename things appropriately in vold:

    e4crypt => fscrypt
    ext4enc => fscrypt
    Ext4Crypt => FsCrypt
    EXT4_* => FS_*
    ext4_encryption_key => fscrypt_key

Additionally, the common functions shared by 'vold' and 'init' are now
in libfscrypt rather than ext4_utils.  So update vold to link to
libfscrypt and include the renamed headers.

Note: there's a chance of 'fscrypt' being confused with the dm-crypt
based encryption code in vold which is called 'cryptfs'.  However,
fscrypt is the name used in the kernel for ext4/f2fs/ubifs encryption,
and it's preferable to use the same name in userspace.

Test: built, booted device with f2fs encryption
Change-Id: I2a46a49f30d9c0b73d6f6fe09e4a4904d4138ff6
diff --git a/FsCrypt.h b/FsCrypt.h
new file mode 100644
index 0000000..16e2f9a
--- /dev/null
+++ b/FsCrypt.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <string>
+
+#include <cutils/multiuser.h>
+
+bool fscrypt_initialize_global_de();
+
+bool fscrypt_init_user0();
+bool fscrypt_vold_create_user_key(userid_t user_id, int serial, bool ephemeral);
+bool fscrypt_destroy_user_key(userid_t user_id);
+bool fscrypt_add_user_key_auth(userid_t user_id, int serial, const std::string& token,
+                               const std::string& secret);
+bool fscrypt_fixate_newest_user_key_auth(userid_t user_id);
+
+bool fscrypt_unlock_user_key(userid_t user_id, int serial, const std::string& token,
+                             const std::string& secret);
+bool fscrypt_lock_user_key(userid_t user_id);
+
+bool fscrypt_prepare_user_storage(const std::string& volume_uuid, userid_t user_id, int serial,
+                                  int flags);
+bool fscrypt_destroy_user_storage(const std::string& volume_uuid, userid_t user_id, int flags);
+
+bool fscrypt_destroy_volume_keys(const std::string& volume_uuid);