libftdi: bump to version 0.20

Needed for openocd 0.7.0 (added in the next commit).

NOTE: There is also a libftdi 1.0 version, but since openocd only needs
0.20 I didn't bother. libftdi 1.0 uses CMake build system.
openocd: bump to version 0.7.0

OpenOCD 0.7.0 has grown a dependency on libusb1.
openocd: update homepage

The old one still works, but it redirects to the new one:
http://openocd.sourceforge.net/