* src/devices/grolbp/lbp.cc: Replace `300' with `font::res' where

* src/devices/grolbp/lbp.cc: Replace `300' with `font::res' where
appropriate.
(DEFAULT_LINEWIDTH_FACTOR): New macro.
(linewidth_factor): New global variable.
(lbp_printer::set_line_thickness): Fix case for size < 0, using
linewidth_factor.
(long_options): Add -w/--linewidth option.
(usage): Updated.
(main): Handle -w option to set linewidth_factor.
(lbp_printer::lbp_printer): Initialize req_linethickness, not
line_thickness.

* src/devices/grolbp/grolbp.man, NEWS, doc/webpage.ms: Updated.

Fixed a bug in the line thickness setting code.

* src/devices/grolbp/lbp.cc (lbp_printer::req_linethickness): New
variable.
(lbp_printer::set_line_thickness): Pass environment as second
parameter.
Implement it actually.
(lpb_printer::set_char, lbp_printer::draw): Use `req_linethickness'
and `set_line_thickness, depending on the current font size.