Reduced the number of focus changes in the outline (#337).
Updated images in the outline; added `showmethodindicator` option (#337).
Added option for not/showing anonymous functions in the outline (#337).
Added `showonefile` option for the outline to always show one file (#337).
Renamed `markvars` method used in spec files to `marksymbols`.
Updated C-based specs to use `marksymbols` to provide outline for C functions.