Log Message:
Update to sitecopy-0.16.6
As per PR/42962 provided by Ivan "Rambius" Ivanov.
While here, update MASTER_SITES

Changes since 0.16.2:

Changes in release sitecopy 0.16.6, 16 July 2008

    * DAV: Fix crash with progress bar enabled with neon 0.27/0.28.

Changes in release sitecopy 0.16.5, 16 July 2008

    * DAV: Fix SSL cert caching to avoid repeated prompts.
    * Update to neon 0.28.3 and support neon 0.24.x through 0.28.x.

Changes in release sitecopy 0.16.3, 12 March 2006

    * DAV: Add PKCS#12 client cert support; "client-cert /path/to/cert.p12"
    * Update to neon 0.26.0 (0.24.x and 0.25.x still supported).