This reverts commit 77c51c5a6b.

Having multiple clipboards are useful, for example for plumber scripts.
I've discussed this on IRC and it is useful to have.

Thanks to tarug0 for the suggestion/patch.

st currently does not keep any mode for the cursor that was active
in the underlying glyph (e.g. italic text), the mode is always
ATTR_NULL [1].  At [2] you can find a screenshot that shows the
implications.  Other terminals (at least vte-based, such as
XFCE-terminal) keep some modes for the cursor.  I find the current
behaviour very disruptive, so here is a patch that keeps a few
(arbitrarily chosen) modes for the cursor.

[1] http://git.suckless.org/st/tree/st.c#n3963
[2] http://i.imgur.com/R2yCEaC.png

This is used by, e.g., tmux.