Add support for multi-user decryption

* Add CLI support using the command "twrp decrypt <PASSWORD> [USER ID]"
* Add GUI support using the menu Advanced --> Decrypt User

multiuser: Parse users only when Decrypt_DE runs successfully

multiuser: Warn when not all users are decrypted

Change-Id: Ia5e943b13c2d5ec5c34ae97661133c19ff471e6d
diff --git a/gui/gui.hpp b/gui/gui.hpp
index d5b9553..7e4ee4e 100644
--- a/gui/gui.hpp
+++ b/gui/gui.hpp
@@ -28,6 +28,7 @@
 void gui_err(const char* text);
 void gui_highlight(const char* text);
 void gui_msg(Message msg);
+void gui_err(Message msg);
 
 std::string gui_parse_text(std::string inText);
 std::string gui_lookup(const std::string& resource_name, const std::string& default_value);