Add dependency on libpng-dev & libjpeg-dev

Without these some plugins aren't built, e.g. gloverlay.

Change-Id: If0c0218eb3b2d0e568a7194a885149b1c171c369
diff --git a/debian/control b/debian/control
index 5a7ae07..29594b5 100644
--- a/debian/control
+++ b/debian/control
@@ -6,7 +6,7 @@
            Sebastien Bacher <seb128@debian.org>,
            Sebastian Dröge <slomo@debian.org>,
            Sjoerd Simons <sjoerd@debian.org>
-Build-Depends: libgstreamer1.0-dev (>= 1.14.4), libasound2-dev (>= 0.9.0) [linux-any] , libgudev-1.0-dev (>= 143) [linux-any], autotools-dev, automake (>= 1.14), autoconf (>= 2.69), libtool (>= 2.2.6), dh-autoreconf, autopoint (>= 0.17), cdbs (>= 0.4.93~), debhelper (>= 10), gnome-pkg-tools (>= 0.7), pkg-config (>= 0.11.0), libxv-dev (>= 6.8.2.dfsg.1-3), libxt-dev (>= 6.8.2.dfsg.1-3), libvorbis-dev (>= 1.0.0-2), libcdparanoia-dev (>= 3.10.2) [!hurd-i386], liborc-0.4-dev (>= 1:0.4.24), libpango1.0-dev (>= 1.16.0), libtheora-dev (>= 1.1), libglib2.0-dev (>= 2.40), zlib1g-dev (>= 1:1.1.4), libvisual-0.4-dev (>= 0.4.0), dpkg-dev (>= 1.15.1), iso-codes, libgtk-3-dev (>= 3.10), zlib1g-dev, libopus-dev (>= 0.9.4), libgl1-mesa-dev, libegl1-mesa-dev, libgles2-mesa-dev, libgraphene-1.0-dev
+Build-Depends: libgstreamer1.0-dev (>= 1.14.4), libasound2-dev (>= 0.9.0) [linux-any] , libgudev-1.0-dev (>= 143) [linux-any], autotools-dev, automake (>= 1.14), autoconf (>= 2.69), libtool (>= 2.2.6), dh-autoreconf, autopoint (>= 0.17), cdbs (>= 0.4.93~), debhelper (>= 10), gnome-pkg-tools (>= 0.7), pkg-config (>= 0.11.0), libxv-dev (>= 6.8.2.dfsg.1-3), libxt-dev (>= 6.8.2.dfsg.1-3), libvorbis-dev (>= 1.0.0-2), libcdparanoia-dev (>= 3.10.2) [!hurd-i386], liborc-0.4-dev (>= 1:0.4.24), libpango1.0-dev (>= 1.16.0), libtheora-dev (>= 1.1), libglib2.0-dev (>= 2.40), zlib1g-dev (>= 1:1.1.4), libvisual-0.4-dev (>= 0.4.0), dpkg-dev (>= 1.15.1), iso-codes, libgtk-3-dev (>= 3.10), zlib1g-dev, libopus-dev (>= 0.9.4), libgl1-mesa-dev, libegl1-mesa-dev, libgles2-mesa-dev, libgraphene-1.0-dev, libpng-dev, libjpeg-dev
 Standards-Version: 3.9.8
 Vcs-Git: https://salsa.debian.org/gstreamer-team/gst-plugins-base1.0.git
 Vcs-Browser: https://salsa.debian.org/gstreamer-team/gst-plugins-base1.0/