Added more metric grids

[whitis]

This patch adds more metric grids. The existing
selection was not sufficient, particularly given that
the program does not allow you to enter a grid spacing
from the keyboard. This patch can be applied to
/usr/local/share/pcb-menu-.res after compilation but if
you recompile the program you will want to patch
/usr/local/src/pcb-20040903/src/pcb-menu.res or you
will lose your changes during make install.

[whitis (whitis-users-sf)]

I have added more grids, both metric and imperial, to the
previous version of the patch. This patch must be applied
in addtion to, not instead of, the first patch. You will
also want the metric display patch.

Some Grids added in this version were some "sensible" grid
sizes divided by two. This is often necessary because a
part is defined with, say 25mil spacing but defined in terms
of a center point resulting in a 12.5mil grid. This is
very common.

Also added were standard lead pitches used on ICs and
connectors.
Surface mount IC pitches of: 0.65mm, 0.635mm, 0.5mm, and
0.4mm, and 0.3mm were added (as well as half values where
not already existing). And 2.5mm, which is a popular
connector grid spacing, was added. 0.635, 1.27mm and
2.54mm were not added as they are the same as 25mil, 50mil
and 100mil, respectively.

Availible grids with both patches applied:
mils: 0.1, 0.5, 1, 2.5, 5, 10, 12.5, 25, 50, 100
mm: 0.01, 0.02, 0.025, 0.5, 0.1, 0.15, 0.2, 0.25, 0.3,
0.325, 0.4, 0.5, 0.65, 1, 2, 2.5, 5mm

[nobody (nobody-users)]

The program has always allowed you to enter a grid spacing
from the keyboard. Some might still like this patch for
easy selection from the menu; for me it makes the menu too
overloaded.

[DJ Delorie (djdelorie)]

maybe we could add a "More..." option at the end of the current list, and have a submenu with the less frequently used grids on it?