fix for a copy-and-paste error in gerbmerge-1.8 which created small alignment issues

gistfile1.diff

diff -u -r gerbmerge-1.8-pristine/gerbmerge/gerbmerge.py gerbmerge-1.8/gerbmerge/gerbmerge.py
--- gerbmerge-1.8-pristine/gerbmerge/gerbmerge.py	2011-06-09 06:07:55.000000000 +0800
+++ gerbmerge-1.8/gerbmerge/gerbmerge.py	2012-11-26 16:20:05.526473454 +0800
@@ -158,7 +158,7 @@
     else:
       x = MaxXExtent + x
     if y>=0:
-      y += OriginX
+      y += OriginY
     else:
       y = MaxYExtent + y
     fid.write('X%07dY%07dD03*\n' % (util.in2gerb(x), util.in2gerb(y)))