curl: Skip check for inet_pton on Windows

Re-apply part of the logic from commit v2.8.0~802 (ENH: allow for shared
build of libcurl ..., 2009-04-10) to skip inet_pton on Windows.  On
versions of Windows prior to Vista the function is not available at
runtime.

Utilities/cmcurl/CMakeLists.txt

@@ -29,6 +29,13 @@ set(DISABLED_THREADSAFE OFF CACHE INTERNAL "Curl can use thread-safe functions")
 set(ENABLE_IPV6 OFF CACHE INTERNAL "Curl IPv6 support")
 set(HTTP_ONLY OFF CACHE INTERNAL "Curl is not http-only")
 
+# Windows Vista and above have inet_pton, but this will link on
+# older versions and then the executable will fail to launch at
+# runtime on older versions because no DLL provides the symbol.
+if(WIN32)
+  set(HAVE_INET_PTON 0 CACHE INTERNAL "Do not use inet_pton")
+endif()
+
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