Small reorganization.

Small reorganization.

I am not sure I fully understand the pending_newline/unskip_newline
logic (which seems mainly related to rtl writing), so I prefer to
leave it alone, in the sense that now things go again as in 2.1
until the point where those booleans are used for producing output.
If it turns out that a spurious (and unwanted) empty line comes
from the previous code, it can be easily corrected later.

I am also reintroducing the check about a separator inset at the end
of the paragraph, because that is necessary for the plain version.