Move create_tempfile() to tempfile.c out of util.c. This means dumpcap

Move create_tempfile() to tempfile.c out of util.c.  This means dumpcap
no longer needs util.c, so it no longer includes routines that use
host_ip_af(), so it no longer needs to define its own host_ip_af().

That also means dumpcap.c no longer needs to include <sys/socket.h>.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@17278 f5534014-38df-0310-8fa8-9805f1628bb7