running non-verax tests
fixed overflow errors

% go test -run TestEnmarshalVarbind
./marshal_test.go:263: constant 4294967295 overflows int
./verax_test.go:159: constant 4294967295 overflows int
FAIL    _/home/sonia/go/bpl-poller/src/github.com/soniah/gosnmp [build
failed]
add dummy decls
Add slog init to all tests - discard and verbose.
manual decodes; request_type, pdu_type, pdu_value fields
marshalVarbind - Integer - rough cut

working up to marshalMsg and TestEnmarshalMsg,
therefore need to refactor Get into Get/Set.
Get/Set/send interface; all TestEnmarshal* passing
rename requesttype/messagetype to pdutype per RFCs
move send() out of gosnmp.go (public interface)