(Re-)setup indent guide lines on for missing autocommands

[ohcibi]

The setup was not redone on BufEnter and TerminalOpen|TermOpen which
made the plugin ignore the indentLIne_*Exclude and probably also the
indentLine_FileType configuration option in some situations.
Possibly a fix for #297

[stsewd]

This fixes the problem where it ignores terminal buffers! Thanks! Would be great to have this merged

[Yggdroot]

BufEnter is almost a duplicate of BufWinEnter, the function will be called twice every time a buffer is entered. I don't want to have the slowdown.

[ohcibi]

@Yggdroot the exclude filetypes/buftypes feature is broken without it. Do you have another idea? Why is BufWinEnter needed? We could remove that since instead.

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[Yggdroot]

BufWinEnter is necessary to support modeline.

[ohcibi]

Then we need to split up that functionality. BufWinEnter is not called in every necessary situation. The documentation clearly recommends BufEnter for filetype specific settings. Since this is about excluding file types it should be called there.

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[Yggdroot]

So we can save the &shiftwidth and &tabstop to buffer-local variables when BufWinEnter is triggered. Use the variables when BufEnter is triggered.