Track backup and restore progress

Track backup and restore progress based on the sizes of the files
as they are being added to the tar backup file. Update the
progress bar based on the sizes of the files.

Change-Id: Idf649efa1db3e91830b4b2add86203a3f30042ff
diff --git a/twrp-functions.hpp b/twrp-functions.hpp
index ff11763..284a297 100644
--- a/twrp-functions.hpp
+++ b/twrp-functions.hpp
@@ -50,6 +50,7 @@
 	static int Try_Decrypting_File(string fn, string password); // -1 for some error, 0 for failed to decrypt, 1 for decrypted, 3 for decrypted and found gzip format
 	static unsigned long Get_File_Size(string Path);                            // Returns the size of a file
 	static std::string Remove_Trailing_Slashes(const std::string& path, bool leaveLast = false); // Normalizes the path, e.g /data//media/ -> /data/media
+	static vector<string> split_string(const string &in, char del, bool skip_empty);
 	static void install_htc_dumlock(void);                                      // Installs HTC Dumlock