Add a patch for memcached to ccache along with a slave devel/ccache-memcached port.
This patch is not safe for WITH_CCACHE_BUILD support yet as that causes all ports to depend on devel/ccache. Enabling that patch would then cause the new devel/libmemcached dependency to require devel/ccache which is a cyclic dependency. The autoconf dependency also causes issues. Add a devel/ccache-memcached slave port that would allow a user to use the ccache+memcached package manually with ports without WITH_CCACHE_BUILD. This patch comes from https://github.com/ccache/ccache/pull/58 and has been an ongoing effort over a few years to be merged into the mainline of ccache. Documenation for it can be found in the MANUAL file at: /usr/local/share/doc/ccache/MANUAL.txt Sponsored by: Dell EMC Isilon