Allow hex format for integer types.

Hello,

Currently I'm missing the ability of integers in xml documents to be 
defined in hex format (e.g. 0x20003cd9). In engineering environments hex 
format is much more common and readable than the decimal format.

But I guess that would mean a change in the xml spec and not in the schema 
spec.

Kind regards,

Wout de Zeeuw

Philips Medical Systems, EasyVision
Room:                 QV-123
Phone:                040-2764094
e-mail:                wout.de.zeeuw@philips.com