Switch back to b2g/ics_strawberry branch

Change-Id: I0e88af707f0fce0d2071d25c142aab21618cdcf8
Point libpng and frameworks/av to our forks

This is necessary for:

frameworks/av : https://bugzilla.mozilla.org/show_bug.cgi?id=911548 

libpng : https://bugzilla.mozilla.org/show_bug.cgi?id=915201
Merge branch 'master' of https://git.mozilla.org/b2g/b2g-manifest into default