Rich text files have groupings of text, where styles are pushed onto
the stack when encountering a start of the group, then popped at the
end of the group.  This was being handled improperly before, because a
single styleChanged flag was being stored to keep track of whether the
style needed to be restored at the end of a group. This fails to work
properly since the single flag isn't keeping track of all the levels
of the stack, so some styles are not restored properly.

When a colour table entry is empty, then the default colour is used.
For an incomplete colour table entry 0 is used for the missing colours.

Previously the -1 value used internally for missing colours was being
converted into white, where it should be using the default colour that
is normally black.

This bug could be seen by loading the following rich text into wordpad:
{\rtf{\colortbl;;}\cf1 text}

user32/tests: Show that Windows avoids creating loops in a menu tree, probably by limiting the depth of such tree.

Previously after initial window creation of a richedit control with the
ES_DISABLENOSCROLL window style flag the scrollbar would be shown but
not disabled.  This patch fixes this issue by explicitly disabling and
showing the scrollbar.

Apparently this is an expensive operation for certain drivers, even if the
binding doesn't actually change.

When the richedit control is created without the ES_AUTOHSCROLL or the
ES_AUTOVSCROLL, then scrolling isn't done automatically when moving the
cursor with the arrow keys, drag selecting with the mouse, or even from
using the EM_SCROLLCARET (based on testing using a modified version of
wordpad).