Broaden scope of gAborting. Fixes hang in HandleUnexpectedSignal.

Change-Id: I4c29cd7b67f07bb9f99c308feac5a3d6c236bc2b
diff --git a/src/logging.h b/src/logging.h
index 75782d5..d0d35ea 100644
--- a/src/logging.h
+++ b/src/logging.h
@@ -318,6 +318,11 @@
 };
 
 extern LogVerbosity gLogVerbosity;
+
+// Used on fatal exit. Prevents recursive aborts. Allows us to disable
+// some error checking to ensure fatal shutdown makes forward progress.
+extern bool gAborting;
+
 extern void InitLogging(char* argv[]);
 
 extern const char* GetCmdLine();