Add routines vfprintf_stderr() and fprintf_stderr() to print to the

Add routines vfprintf_stderr() and fprintf_stderr() to print to the
standard error and, in Wireshark on Windows, create a console if
necessary.  Have the cmdarg_err routines use them.

Use *fprintf_stderr() to print the output of -L, rather than using
cmdarg_err_cont(), so that we don't get extra newlines in the output (it
should look similar to the output of tcpdump).

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@32711 f5534014-38df-0310-8fa8-9805f1628bb7