efl: add dependency on libunwind

* optional dependency added to efl in:
  commit 664708b817ab0cdc7177df3743b5d9c9ab7dd2b0
  Author: Carsten Haitzler (Rasterman) <raster@rasterman.com>
  Date:   Tue May 5 11:35:16 2015 +0900
  Subject: eina - start a much improved eina dbug infra and have eina_log use it
* fixes:
efl-1.15.1: edje rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-input-evas rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: eo rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: libeet rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: efreet-trash rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-ipc rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: eina rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-x rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: emotion rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-imf-evas rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: libemotion rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: efl rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-input rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-file rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ethumb rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-con rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: evas rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: efreet-mime rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: eeze rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: libefreet rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: embryo rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-evas rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-imf rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: ecore-audio rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: eldbus rdepends on libunwind, but it isn't a build dependency? [build-deps]
efl-1.15.1: eio rdepends on libunwind, but it isn't a build dependency? [build-deps]
enjoy-0.1.0+gitrAUTOINC+aa8fec69e8: enjoy rdepends on libunwind, but it isn't a build dependency? [build-deps]

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>