Put the stuff to get the sized integer types defined into pcap-types.h.

Put the stuff to get the sized integer types defined into pcap-types.h.

Have pcap-types.h arrange to define the intN_t/u_intN_t types, and the
INTn_MAX/UINTn_MAX values, on all platforms, and use it wherever it's
appropriate.

Include it up front in scanner.l, to avoid redefinitions of the
INTn_MAX/UINTn_MAX types.