Update ettercap to 0.7.5.1.

* Ettercap now uses cmake system. Drop pkg-config requirement.
* Depends on curl in homebrew as minimum requirement is now 7.26.0.
* Depends on ghostscript for pdf generation when building.
* Merge upstream fix for CVE-2012-0722.
* Merge upstream fix for clang build.

Closes #16983.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>