LibGMP Update

LibGMP has been updated to the latest version 6.1.2. Also with this updates comes the default use of assembly optimisations for both 32 and 64 bit systems. This results in considerable performance improvements to the library. To correspond with this both nettle and gnutls have a new dash release which uses the updates to the newest libgmp version dependency. As always the latest releases are available on the Projects page while still allowing access to any previously supported releases. The latest FFmpeg build has also been updated to use the latest versions of the new libraries as well.