Header refactoring: break out rb.h dependencies

include/jemalloc/internal/prof_structs.h

@@ -1,6 +1,8 @@
 #ifndef JEMALLOC_INTERNAL_PROF_STRUCTS_H
 #define JEMALLOC_INTERNAL_PROF_STRUCTS_H
 
+#include "jemalloc/internal/rb.h"
+
 struct prof_bt_s {
 	/* Backtrace, stored as len program counters. */
 	void		**vec;