FTP: Adds support for IPv6 and fixes various transfer issues
* netutils/ftpd: Fix support for IPv6 FTP server
* netutils/ftpc:Adds support for IPv6 sockets
* ftpc: Must convert port received by EPSV reply to network order
* ftpc: Data socket address for passive connection should be same as server address
* ftpc: Must skip human readable string in EPSV response before scanning for port
* ftpc: Don't send PASS command if USER command was sufficient. ie no password required
* ftpc: Generically handle permanent negative completion in shard ftpc_cmd logic
* ftpc: Minor addresssing fix
* ftpc: Tweak logic for overriding network debugging output
* FTP: Adds option for setting stack size of various threads in FTPD and FTPC
* netutils/ftpd: Fixes build error setting IPv4 address. sin_addr => sin_addr.s_addr
* netutils/ftpd: Protects against partial write returns by looping in that case
Approved-by: Gregory Nutt <gnutt@nuttx.org>
