This is the 'multiple pdb backends' patch from ctrlsoft, aka Jelmer Vernooij

This is the 'multiple pdb backends' patch from ctrlsoft, aka Jelmer Vernooij
<jelmer@nl.linux.org>.

This patch also includes major rework of pdbedit to use popt, and the addition
of -i paramter (allowing the user to specify which PDBs is being
operated on) and -e to export a pdb - useful for backup and testing etc.

Use of -i and -e gets us pdb2pdb functionality for transition between backends,
much like the sam2sam in TNG.

Andrew Bartlett
(This used to be commit c10def37f506d3f2bab442418ac08fdb62659b02)