mDNSResponder: Update to v765.1.2

The sources can be obtained via:

https://opensource.apple.com/tarballs/mDNSResponder/mDNSResponder-765.1.2.tar.gz

Move mDNS_StartResolveService() and mDNS_StopResolveService() to an
RTEMS-specific file (rtemsbsd/mdns/mDNSResolveService.c) using the
v576.30.4 implementation.  Apple removed these functions without
explanation.

Update #3522.

mDNSResponder/unittests/InterfaceTest.c

@@ -0,0 +1,19 @@
+#include "InterfaceTest.h"
+#include "mDNSEmbeddedAPI.h"
+
+
+NetworkInterfaceInfo *intf;
+mDNS *m;
+
+int LocalSubnetTest(void);
+
+UNITTEST_HEADER(InterfaceTest)
+    UNITTEST_TEST(LocalSubnetTest)
+UNITTEST_FOOTER
+
+UNITTEST_HEADER(LocalSubnetTest)
+    // need a way to initialize m before we call into the class of APIs that use a ptr to mDNS
+    // should that pointer be common to all tests?
+    // mDNS_AddressIsLocalSubnet(mDNS *const m, const mDNSInterfaceID InterfaceID, const mDNSAddr *addr)
+    // TEST_ASSERT_RETURN (for IPv4/IPv6 local subnet)
+UNITTEST_FOOTER