Slightly improved Linux/BSD documentation

I slightly improved the Linux/BSD compilation instructions:
- Added information that the procedure has been tested with XUbuntu 13.10 (I just followed the Debian/Ubuntu/Spinoff part, clarified the pthread problem and was able to start oracle+Cockatrice)
- Added FreeBSD 10.0 (compared to FreeBSD 9 it uses a new package system but the packages are still the same; Compiling worked, I didn't test the Build due to a lack of a graphical desktop) and added libgcrypt dependency for Servatrice on FreeBSD 10 (which also appears on Linux systems and is implied in the CentOS howto).

Unlike with the Windows doc update, no problems occured :-)