libsigc++: add hash file

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libsigc/libsigc.hash

@@ -0,0 +1,2 @@
+# From http://ftp.gnome.org/pub/gnome/sources/libsigc++/2.2/libsigc++-2.2.11.sha256sum
+sha256	9834045f74f56752c2c6b3cdc195c30ab8314ad22dc8e626d6f67f940f1e4957	libsigc++-2.2.11.tar.xz