release: prepare for release of 0.7.7
osx: update homebrew recipe

The patch is not needed anymore. We replace it with the appropriate
`./configure` option. We could use the shipped launchd file but it
does not contain provision to specify options to enable SNMP support.
redhat: fix version in lldpd.spec
redhat: don't try to install systemd stuff

I don't know how I should handle this. Let somebody with better
knowledge tell me how to install systemd in the .spec file.