Comment 6 for bug 699454

This is the latest version of the patch.
I removed notes on my changes from gerber.c, so the patch
could be applied to CVS. I also corrected some spaces and
added maximum coordinates detection (e.g. when mm units are
requested and the board is larger than 100 mm, it is incorrect
to write `%FSLAX24Y24*%' - there should be something like
`%FSLAX34Y34*%').

Tests showed that --outline-gerbers option
was buggy: it used to output a lot of unused (and invalid)
apertures into every Gerber file; I fixed this issue, too.

The resulting commit message could look like this:

Add more output options:

(1) metric output (separately in Gerbers and Excellons)
(2) 0..6 precision both in metric Excellon output
    and (separately for X and Y axes) in Gerber
(3) decimal point in Excellon output
(4) outline every Gerber
(5) don't round drill diameters
(6) export empty layers, too
    (based on Bert Timmerman lambert63 patch 1833934)
(7) digits before the decimal point are autodetected
    (e.g. specify 3.x format when the maximum coordinates are
     less than 1000 and more than 100)

Fix bug [2162834]
Add URLs to Gerber and Excellon descriptions in comments