- Added the am_zoom command to zoom the automap by a specific step and set default mouse wheel

bindings for it. I'm not sure how this should be exposed through the menu, however. Technically,
  it's different from the pan keys, but from an end user's point of view, they both zoom the
  automap, so they should both be listed under the Zoom in and out controls. But the menu code
  can't handle that.

SVN r2663 (trunk)

src/c_bind.cpp

@@ -188,6 +188,8 @@ static const FBinding DefAutomapBindings[] =
 	{ "=", "+am_zoomin" },
 	{ "kp-", "+am_zoomout" },
 	{ "kp+", "+am_zoomin" },
+	{ "mwheelup", "am_zoom 1.2" },
+	{ "mwheeldown", "am_zoom -1.2" },
 	{ NULL }
 };