test: simplify deps for fuzzer entrypoint

No need to depend on the rest of the test code (ares-test.h) for
the fuzzer entrypoint; this makes the entrypoint slightly simpler
to build with LLVM's libFuzzer.

Also shift the code to effectively be C rather than C++

test/ares-test-fuzz.cc

@@ -1,44 +1,48 @@
-#include "ares-test.h"
-#include <vector>
+#include <stddef.h>
+
+#include "ares.h"
 
 // Entrypoint for Clang's libfuzzer
-extern "C" int LLVMFuzzerTestOneInput(const unsigned char *data,
+#ifdef __cplusplus
+extern "C"
+#endif
+int LLVMFuzzerTestOneInput(const unsigned char *data,
                                       unsigned long size) {
   // Feed the data into each of the ares_parse_*_reply functions.
-  struct hostent *host = nullptr;
+  struct hostent *host = NULL;
   struct ares_addrttl info[5];
   int count = 5;
   ares_parse_a_reply(data, size, &host, info, &count);
   if (host) ares_free_hostent(host);
 
-  host = nullptr;
+  host = NULL;
   struct ares_addr6ttl info6[5];
   count = 5;
   ares_parse_aaaa_reply(data, size, &host, info6, &count);
   if (host) ares_free_hostent(host);
 
-  host = nullptr;
-  ares::byte addrv4[4] = {0x10, 0x20, 0x30, 0x40};
+  host = NULL;
+  unsigned char addrv4[4] = {0x10, 0x20, 0x30, 0x40};
   ares_parse_ptr_reply(data, size, addrv4, sizeof(addrv4), AF_INET, &host);
   if (host) ares_free_hostent(host);
 
-  host = nullptr;
+  host = NULL;
   ares_parse_ns_reply(data, size, &host);
   if (host) ares_free_hostent(host);
 
-  struct ares_srv_reply* srv = nullptr;
+  struct ares_srv_reply* srv = NULL;
   ares_parse_srv_reply(data, size, &srv);
   if (srv) ares_free_data(srv);
 
-  struct ares_mx_reply* mx = nullptr;
+  struct ares_mx_reply* mx = NULL;
   ares_parse_mx_reply(data, size, &mx);
   if (mx) ares_free_data(mx);
 
-  struct ares_txt_reply* txt = nullptr;
+  struct ares_txt_reply* txt = NULL;
   ares_parse_txt_reply(data, size, &txt);
   if (txt) ares_free_data(txt);
 
-  struct ares_soa_reply* soa = nullptr;
+  struct ares_soa_reply* soa = NULL;
   ares_parse_soa_reply(data, size, &soa);
   if (soa) ares_free_data(soa);
   return 0;