Create the other side of conversion chain when IM is banned (bug #12646).

We allow png, jpg to channel through already existing tiff2ps (library
libtiff-tools). Other formats can be added if there is a request.

For future reference:
- using pnmtops seem to have issues with landscape/portrait flip, so
  tiff2ps seems better alternative.
- using GraphicsMagick won't help because some distros ban postscript
  processing directly in its code (e.g. openSUSE)

This patch finishes IM policy ban handling, we can't probably do much
better.

lib/configure.py

@@ -1206,8 +1206,10 @@ def checkConverterEntries():
         except:
             removeFiles(['mock.eps'])
             #needs empty record otherwise default converter will be issued
-            rc_entry = r'\converter eps        png        ""	""'
-            addToRC(rc_entry)
+            addToRC(r'''\converter eps        png        ""	""
+\converter png        eps        ""	""
+\converter jpg        tiff        "convert $$i $$o"	""
+\converter png        tiff        "convert $$i $$o"	""''')
             logger.info('ImageMagick seems to ban conversions from EPS. Disabling direct EPS->PNG.')
     #
     # no agr -> pdf6 converter, since the pdf library used by gracebat is not