msxml3: Fix varargs handling in libxml2 error callback implementation

[Alexandre Julliard]

Nikolay Sivov <nsivov at codeweavers.com> writes:

> The problem is that vsnprintf() was called multiple times with same
> va_list. Ti fix that it was necessary to get rid of some tracing bits
> like macro-defined callback calls and a single function for all kinds
> of error types.

Actually there's no need to call vsnprintf multiple times. The debug
buffer has a limited size anyway, so we might as well use a limited
stack buffer here.

-- 
Alexandre Julliard
julliard at winehq.org