Apply original patch (netcat-cygwin.patch) for SF issue #50

Issue description:

Netcat 0.7.1 does not compile on Cygwin out of the box.

1) On Windows, there is no ipi_spec_dst in struct in_pktinfo.

Also, when issue (1) is fixed, UDP mode does not work, as:

2) SO_LINGER option is not valid for UDP sockes on Windows
Merge branch 'master' into sourceforge-bug-50

Conflicts:
	src/network.c
Fix AC_CHECK_MEMBERS for in_pktinfo.ipi_spec_dst
Merge branch 'master' into sourceforge-bug-50