Could you please bump libavc1394 to version 0.4.1? This is supposed to contain a lot of bug fixes that makes it quite stable. If you want to correct the style to use econf, just delete out all the functions in the ebuild except src_install. I've tested on 1.4 and it works.
Added as testing. To enable testing ebuilds on your system, add ACCEPT_KEYWORDS="~x86" to your /etc/make.conf.