FileZilla Client is a fast and reliable cross-platform FTP, FTPS and
SFTP client with lots of useful features and an intuitive graphical user
interface.

FileZilla requires wxGTK or wxPython as core dependencies and tinyxml as 
optional package or it can use builtin package

In case you don't have tinyxml requirement, you can use builtin package by 
passing variables to the script (VAR=yes/no ./filezilla.SlackBuild):
TINYXML=yes|no (default: no), requires tinyxml