5261 libm should stop using synonyms.h

@@ -25,11 +25,11 @@
 /*
  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
-#pragma weak casinh = __casinh
+#pragma weak __casinh = casinh
 
 /* INDENT OFF */
 /*
  * dcomplex casinh(dcomplex z);
  * casinh z = -i casin iz .