Add more initializers to quiet a clang warning

[rtereshin]

Summary

struct crashreporter_annotations_t gained one more uint64_t field in
CRASHREPORTER_ANNOTATIONS_VERSION 5

causing an annoying clang warning:

llvm/lib/Support/PrettyStackTrace.cpp:92:65: warning: missing field 'abort_cause' initializer [-Wmissing-field-initializers]
        = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0 };
                                                                ^
1 warning generated

Let's fix it.

Patch by Roman Tereshin

[echristo]

Seems reasonable? Not a fan of the ifdef, but I also don't know what changed in 10.11 here. If it's wrong we can work around it later.

[echristo]

(Also sorry, I thought I'd hit submit on my comments a few days ago, but apparently hit close tab before I'd gotten that far)

[rtereshin]

In D42268#989602, @echristo wrote:

(Also sorry, I thought I'd hit submit on my comments a few days ago, but apparently hit close tab before I'd gotten that far)

@echristo No problem, thank you for looking into this!

[rtereshin]

@dsanders Could you please commit this for me?

Thanks!

lib/Support/PrettyStackTrace.cpp

 // Integrate with crash reporter libraries.
 #if defined (__APPLE__) && defined(HAVE_CRASHREPORTERCLIENT_H)
 //  If any clients of llvm try to link to libCrashReporterClient.a themselves,
 //  only one crash info struct will be used.
 extern "C" {
 CRASH_REPORTER_CLIENT_HIDDEN 
 struct crashreporter_annotations_t gCRAnnotations 
         __attribute__((section("__DATA," CRASHREPORTER_ANNOTATIONS_SECTION))) 
+#if CRASHREPORTER_ANNOTATIONS_VERSION < 5
         = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0 };
+#else
+        = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0, 0 };
+#endif
 }
 #elif defined(__APPLE__) && HAVE_CRASHREPORTER_INFO
 extern "C" const char *__crashreporter_info__
     __attribute__((visibility("hidden"))) = 0;
 asm(".desc ___crashreporter_info__, 0x10");
 #endif
 
 /// CrashHandler - This callback is run if a fatal signal is delivered to the