[xml] libxml2-2.7.8 and MinGW

[Earnie <earnie users sourceforge net>]

I've been building libxml2-2.7.8 and have been having a heck of a time
getting xmlcatalog to work with a shared DLL library.  I've finally
confirmed that the issue is caused by optimizations with -O2 or -O1.  If
I use -O0 the issue goes away.  The effect is the xmlIsPubidChar_tab
array is seen by xmlcatalog to contain all 0x00 values.  I'm using
GCC-4.6.1 and binutils-2.21.53.20110804 as delivered by MinGW.  I wanted
give this list a report of what I've found in the event others come by,
they may have already.

-- 
Earnie
-- https://sites.google.com/site/earnieboyd/