Add support for webp images.

Use magick instead of convert on Linux when present.

makefile: Default compile should use only -Wall for compatibility

lout 3.43

fix many compile warnings

lout 3.43

fix many compile warnings

include/lengths: Remove undefined __loutd reference.

PostScript dg is empty, so PDF __loutd is not needed.
This fixes PDF output of the user manual.
.gitignore: Add *.ldx

Add DESTDIR variable to makefile

This makes it easier for distributions to install to a staging
directory[0].

[0]: https://www.gnu.org/prep/standards/html_node/DESTDIR.html

lout 3.42

lout 3.41

lout 3.40

lout 3.39