rts: fix barf format attribute

Summary: See definition of PRINTF above the change

Reviewers: bgamari, erikd, simonmar, Phyx

Reviewed By: Phyx

Subscribers: Phyx, rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4392

includes/rts/Messages.h

@@ -41,7 +41,7 @@
  */
 void barf(const char *s, ...)
    GNUC3_ATTRIBUTE(__noreturn__)
-   GNUC3_ATTRIBUTE(format(printf, 1, 2));
+   GNUC3_ATTRIBUTE(format(PRINTF, 1, 2));
 
 void vbarf(const char *s, va_list ap)
    GNUC3_ATTRIBUTE(__noreturn__);