More work on holes: added documentation and Postscript output.

- overlap.c (inside, test_overlap): check for instance type 
- overlap.c (inside, test_overlap): support hole instances
- README: put a pointer to the GUI description at the beginning
- README, gui.html: documented role and creation of holes
- inst.h: holes can now link to pads and vice versa
- hole.c, obj.c (instantiate): connect holes with pads and apply consistency 
  checks
- postscript.c: added output for holes
- icons/hole.fig: make hatched surroundings of hole look more round



git-svn-id: http://svn.openmoko.org/trunk/eda/fped@5940 99fdad57-331a-0410-800a-d7fa5415bdb3

gui.html

@@ -222,6 +222,15 @@ Tools are used to add new elements and to manipulate existing ones.
     containing the pad. Move the mouse cursor to the first point, then
     drag to the second point. The pad's name can be edited after selecting
     the pad.
+  <DT><IMG src="manual/hole.png">
+  <DD> Add a hole. There are two purposes for holes:
+    <UL>
+      <LI> Pins of through-hole components. In this case, the hole has to be
+	inside a pad.
+      <LI> Mechanical support. In this case, the hole has to be outside any
+       pads.
+    </UL>
+    The construction of holes is the same as for pads.
   <DT><IMG src="manual/line.png">&nbsp;<IMG src="manual/rect.png">
   <DD> Add a line or a rectangle. Similar to pads, lines and rectangles
     are defined by two points. The width of the line can be edited after