snmptrap and snmpnetstat don't build on cygwin due to optarg

Building 4.2.pre2 on cygwin using the script in the README.win32
I was getting a failure on snmptrap which (looking at nohup.out)
led me to add an "include <getopt.h>" in snmptrap.c and later in
snmpnetstat/main.c which had a similar problem. They compiled
after that but I can't say I've tested them or checked this much.
The line was in some other source files with similar code though.

nohup.out error:

../../apps/snmptrap.c: In function `optProc':
../../apps/snmptrap.c:136: `optarg' undeclared (first use in this function)
../../apps/snmptrap.c:136: (Each undeclared identifier is reported only once
../../apps/snmptrap.c:136: for each function it appears in.)
../../apps/snmptrap.c:139: warning: unreachable code at beginning of switch statement

I think the snmpnetstat error was a little different. It might have
mentioned getopt by name. I don't have output saved anywhere.

Regards,
Ted