Do not include config.h in heimbase.h (fix #447)

We can't include config.h in public headers, as config.h is not public.

This reverts part of commit a8f0905b71.

lib/base/heimbase.c

@@ -34,6 +34,7 @@
  */
 
 #include "baselocl.h"
+#include "heimbase-atomics.h"
 #include <syslog.h>
 
 static heim_base_atomic_integer_type tidglobal = HEIM_TID_USER;