Fix up boldfacing.

Fix up boldfacing.

Different renderers (different *roffs, different -man macro packages,
different man-to-HTML translators, etc.) may handle fonts and paragraph
boundaries differently, or may handle font resetting in .BR and .B
differently, so:

	reset the font at or before the end of a paragraph;

	don't assume that font changes persist across paragraph breaks;

	don't use .B or .BR inside boldfaced text.