rng-tools: remove libgcrypt dependency

Remove libgcrypt dependency, spotted by buildbot.
It seems to be related to x86-only functionality.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
dump1090: Update to latest version.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Merge pull request #129 from hnyman/fix-rng-tools

rng-tools: remove libgcrypt dependency