Bug 858619 - GC: Address rooting hazards in ctypes r=terrence

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extra : rebase_source : 04bd30cebc35e48feaaf06a36603da3747ad6f9f
bug 832524 pt 2 - position of the menu gutter rule in the app menu needs to be sensitive to resolution. r=dao
bug 832524 pt 3 - use higher-resolution menuitem icons when available on hidpi display. r=dao