Fix build issues with the OpenFlow printer on some systems.

Don't assume we have <stdint.h>.  Instead, use the AC_TYPE_ macros to
ensure we have the C99 intN_t and uintN_t types; we already include
<inttypes.h> in tcpdump-stdinc.h iff we have it.

Get rid of the structure declarations in openflow-1.0.h, as they have
zero-length arrays (not supported by all the compilers people might be
using) and as

	1) they're only used in sizeof()

and

	2) after each one there's an assertion to check that sizeof()
returns a specific numerical value

so, instead, just #define various _LEN items to those numerical values
and use them.

Add an openflow.h header with a #define for the length of the basic
header, and move the declaration of of10_header_body_print() there.