Be more selective about turning off deprecation warnings.

Only turn them off in the vicinity of those nasty cross-platform APIs.

(This also checks in the generated Kerberos dissector, which we forgot
to do in the last checkin.)

Change-Id: I5dc9162ff64afe764e37866706590ed2ed965acb
Reviewed-on: https://code.wireshark.org/review/3882
Reviewed-by: Guy Harris <guy@alum.mit.edu>