upgrade to wx2.5.4

Hi friends,

wx2.5.4 is somewhat incompatible to 2.5.3, regarding those casting
orgies performed currently to call wxEvtHandler::Connect (e.g. in
frmQuery). The new way using wxXXXEventHandler macros is much nicer, and
we'll want to use the forthcoming wx2.6 anyway so we should upgrade to
using 2.5.4 now on all build systems for 1.3.
As soon as this is done, I'll upload the needed pgAdmin patches to use that.

Regards,
Andreas