packaging issue: thirdparty/apple/dnsinfo.h

Missing header reference in Makefile.inc prevents necessary header file from being packaged in official distribution.

Fixes Issue: #763
Fix By: Brad House (@bradh352)

src/lib/Makefile.inc

@@ -109,5 +109,6 @@ HHEADERS = ares__buf.h			\
   ares_str.h				\
   ares_strsplit.h			\
   ares_setup.h				\
-  setup_once.h
+  setup_once.h				\
+  thirdparty/apple/dnsinfo.h