Automatically enable IPv6 if available
Add support for TCP keepalive (-K option)
Add the -K option to help and man page
Fix minor typo in man page
Fix broken UDP support
Merge branch 'keepalive'

Conflicts:
	src/netcore.c
set return value to EXIT_SUCCESS on successful completion of NETCAT_LISTEN mode
Merge branch 'sourceforge-bug-47'
Apply patch for SF issue #57: -L ADDR:PORT optarg processing typo

Issue description:

The "-L" (tunneling) option is implemented with an error in current CVS
version - the colon is zeroed out in the string clone, but the original
is tested as a hostname.
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
Only set SO_LINGER on TCP sockets

SO_LINGER is meaningless for UDP and on some platforms, an attempt to
set that option on a UDP socket triggers an error (see Sourceforge
issues #50, #55 and #56).
Merge branch 'master' into sourceforge-bug-50

Conflicts:
	src/network.c
Fix AC_CHECK_MEMBERS for in_pktinfo.ipi_spec_dst
Apply netcat-cvs-20110926-UDPfix.patch (part 2)

This part fixes build failures on platforms where struct in_pktinfo is
not available.
(cherry picked from commit 6de82cc6790243fc7be52ea0889b7205823ab684)
Merge branch 'master' into sourceforge-bug-50
Merge branch 'sourceforge-bug-50'
Merge branch 'sourceforge-bug-57'
Man page improvements

Include the descriptions of the connect and listen modes (which are
included in the info pages) into the man page as well.
Add some unit tests for the portsrange code

Note that none of them passes, showing that the code is badly broken.
Improve encapsulation of modules

The problem: I want to write a unit test for the functions in
portsrange.c. If the project is configured with --enable-debug, then the
code in portsrange.c depends on the ncprint and debug_fmt functions
which are defined in misc.c. However, misc.c depends on stuff in
netcat.c. On the other hand, netcat.o can't be linked into the unit test
executable because it contains the main function.

The solution: Move the ncprint and debug_fmt functions to a separate
file (ncprint.c) and ensure that it is completely self-contained. In
that case, it is enough to link ncprint.o together with portsrange.o
into the test executable.

Required changes:
* Rename misc.h to ncprint.h (mish.h only contained stuff relevant for
the two functions moved to ncprint.c).
* Make opt_debug and opt_verbose static variables in ncprint.c and
define new functions to set them.