Added a patch libpurple_jabber_parser_error_handler.diff which -may- fix the crash...

Added a patch libpurple_jabber_parser_error_handler.diff which -may- fix the crash seen by us for quite some time which looks like this:
{{{
Thread 0 Crashed:
0   <<00000000>> 	0xfffeff40 objc_msgSend_rtp + 64
1   com.apple.Foundation           	0x92cb1d78 _structuredErrorFunc + 48
2   libxml2.2.dylib                	0x91d60cd8 __xmlRaiseError + 1220
3   libxml2.2.dylib                	0x91d6341c xmlSubstituteEntitiesDefault + 1588
4   libxml2.2.dylib                	0x91d56c94 xmlParseChunk + 560
5   libpurple                      	0x0b48bc0c jabber_parser_free + 68
}}}
as seen in [http://www.smartcrashreports.com/dev/crash.php?id=18c42ee7244c3effb7527f91b6f55d8aadaf1571 this crash report].

A same-looking crash, with a Foundation-supplied structured error function crashing while attempting to message some unknown ObjC object (or messaging random memory which happens to route through `objc_*`), can be found in [http://www.cocoabuilder.com/archive/message/cocoa/2007/2/27/179496 this cocoadev thread].

Perusing the libxml2 2.6.16 code indicates that supplying our own handler should avoid using the system-supplied one. (How the system is supplying one, I'm not sure, since a call to `xmlSetStructuredErrorFunc()` would be necessary, I think).

git-svn-id: svn://svn.adiumx.com/adium/trunk@22039 1c916fce-81e2-0310-a464-8ca513f45935