Include <errno.h> on both Windows and UN*X.

We need <errno.h> on UN*X in some files that include tcpdump-stdinc.h,
such as missing/inet_pton.c.

Remove includes of <errno.h> from files that include tcpdump-stdinc.h.
print-ether: print 'ethertype IEEE1905.1' instead of 'ethertype Unknown'

not a full decoder, uses default print
reference: http://standards.ieee.org/develop/regauth/ethertype/eth.txt
Print an optional packet number in the beginning of line

The new option is '--number'.
man: add new '--number' option
Merge pull request #387 from fxlb/packet-number

Print an optional packet number in the beginning of line
Escape the second - in --number.
Add a --version option, to print just version information.

Also, use #defines starting at 128 (outside the ASCII range) for long
options having no short-option equivalent, and have -h/--help exit with
an exit status of 0 (you just asked for usage information, and you got
it - no fault, no error).
Add --version to the usage message.
Document --version.
date update