doc: help2man: preserve layout of tables

doc: help2man: preserve layout of tables

This is useful in many man pages like date , dd, od, tr, ...
where there are tables presented, where extraneous lines
between each entry are best avoided.

* man/help2man: Use .PD 0 (Paragraph Distance)
to avoid extraneous blank lines within .TP delineated tables.
Also use explicit widths with .TP in such tables,
to preserve the alignment from the --help output.