Mark IsBinaryUpgrade as PGDLLIMPORT to fix windows builds after a7ae1dc.

Author: David Rowley

Author: anarazel

src/include/miscadmin.h

@@ -134,7 +134,7 @@ extern pid_t PostmasterPid;
 extern bool IsPostmasterEnvironment;
 extern PGDLLIMPORT bool IsUnderPostmaster;
 extern bool IsBackgroundWorker;
-extern bool IsBinaryUpgrade;
+extern PGDLLIMPORT bool IsBinaryUpgrade;
 
 extern bool ExitOnAnyError;