libxo.3: fix mdoc usage.
libxo.3: fix grammar and punctuation.
xo_emit.3: fix mdoc usage.
xo_create.3: sentences should start on a new line.
xo_create.3: fix mdoc usage.
xo_create.3: grammar fix.
xo_err.3: fix mdoc usage.
mdoc style: start sentences on new lines.
xo_finish.3, xo_flush.3: mdoc cleanup.
xo_format.3: first cleanup pass for mdoc usage, spelling and grammar.
xo_no_setlocale.3, xo_open_container.3: fix mdoc usage, spelling and grammar.
xo_open_list.3, xo_parse_args.3: fix mdoc usage, spelling and grammar.
xo_set_{allocator, flags, info}.3: fix mdoc usage, spelling and grammar.
xo_set_{options, style, writer}.3: fix mdoc usage.
General cleanup of xo.1.
General cleanup of xolint.1.