afc.c: fixed leaks in various functions when an invalid argument error is returned.
cython: Add error codes and messages for LOCKDOWN_E_PAIRING_DIALOG_PENDING and LOCKDOWN_E_USER_DENIED_PAIRING

Change-Id: I159fe465ee964c391c130b756404fb80f56e160a
cython: Don't fail printing an error message with no string description

Change-Id: I571e5f01423b505223ef7a9b1faedcb94011acd3
idevicebackup2: Fix retry loop when device requests 0 files

Under certain circumstances a device could request an empty array
of filenames to be transferred with DLMessageDownloadFiles.
This was not handled correctly in idevicebackup2 by just doing
nothing, resulting in a 'retry loop' waiting endlessly for new
messages from the device.
The solution is to send a termination packet and a success
status response.

Thanks to pondahai for reporting.
common: Fix Win32 linking by adding ws2_32 to libraries
Merge branch 'master' of https://github.com/libimobiledevice/libimobiledevice