The problem here is just that the autoconf ac_pkg_swig.m4 snippet used in the m4 dir of gearman-interface is broken and cannot detect swig versions greater than 1.x.
There is an updated macro available in the latest version of autoconf-archive, which I've asked upstream to include (they do not have a public bug tracker setup). Once I hear back from them, I will prepare an upload with the new m4 macro in place. Its staged here lp:~clint-fewbar/gearman-interface/debian-packaging -- To UNSUBSCRIBE, email to debian-bugs-rc-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org