Patches to fix PNG chart output problem

[John Darrington]

These patches fix the recently reported problem with charts being
emitted black on black.

I'm not totally happy with the way this patch exposes functions 
which were previously known only to the driver, but its the
easiest solution in the short term.

A review before I push them would be appreciated.

J'

-- 
PGP Public key ID: 1024D/2DE827B3 
fingerprint = 8797 A26D 0854 2EAB 0285  A290 8A67 719C 2DE8 27B3
See http://sks-keyservers.net or any PGP keyserver for public key.

0001-New-structure-xr_color.patch
Description: Text Data

0002-Respect-forground-and-background-options-when-writin.patch
Description: Text Data

signature.asc
Description: Digital signature