Add stack to error messages.
Fix browser.xul init in Australis
Make button compatible with Australis panel
OptiPNG
Update maxVersions
Fix about:scriptish script order
Closes #198 - Switch from removed 'sdk/deprecated/observer-service' to
'sdk/system/events' to fix missing module error.

(cherry picked from commit 49b2a5332454bf04a272250872dff5fce1b427ad)
revert button in Australis
Closes #203 GM_* functions stpped working on Nightly
<em:maxVersion>30.*</em:maxVersion> for Fx