[gnome-continuous] manifest: Tag libpng with an explicit commit object

[Emmanuele Bassi <ebassi src gnome org>]

commit 3afe096aeced40872f2d5fc1c6c951baf033a5eb
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Thu Jan 7 17:24:47 2016 +0000

    manifest: Tag libpng with an explicit commit object
    
    The version tags are completely broken after the maintainer did some Git
    surgery that clearly backfired spectacularly.

 manifest.json |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/manifest.json b/manifest.json
index acbb71a..9ab2eb5 100644
--- a/manifest.json
+++ b/manifest.json
@@ -321,7 +321,8 @@
                 "setuid": ["/runtime/usr/libexec/dbus-daemon-launch-helper"]},
 
                {"src": "git:git://libpng.git.sourceforge.net/gitroot/libpng/libpng",
-                "tag": "v1.6.20"},
+                "tag": "047737496a77eeb97f9991919dac08ca3c149711",
+                 "tag-reason": "The version tags are completely borked and point to weird commits"},
 
                {"src": "fd:cairo",
                 "config-opts": ["--disable-interpreter"]},