Configure whether we have WinPcap based on whether WINPCAP_VERSION is

Configure whether we have WinPcap based on whether WINPCAP_VERSION is
set in the config.nmake file.

Configure whether we have pcap_findalldevs() based on whether
WINPCAP_VERSION is 2.3 (if so, we don't) or 3.0 or 3.1 (if so, we do).

WinPcap 3.0 has the new libpcap declarations of "pcap_lookupnet()" and
"pcap_open_live()" in which the first argument is a "const char *"
rather than a "char *"; declare the functions and pointers to them
appropriately based on the version of WinPcap.

If we don't have pcap_findalldevs(), don't declare a pointer to it, as
we don't have a declaration of pcap_if_t.

We also need to refer to "pcap_freealldevs()", so make a pointer for it.

"symbols[]" is a const array; make the pointer to elements in it a const
pointer.

Fix some typoes.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@8660 f5534014-38df-0310-8fa8-9805f1628bb7