lldpd 0.7.6

Update lldpd to 0.7.6. This version is compatible with Mac OS X 10.6.

A patch is needed to avoid the installation of a provided launchd plist file outside the prefix. I will keep the patch at its current location until it is not needed by the formula currently in homebrew but I can also moved it to a gist if it is considered as a better practice.