spelling

--- a/src/Tools/Code/code_simp.ML	Fri Jan 03 14:38:13 2014 +0100
+++ b/src/Tools/Code/code_simp.ML	Fri Jan 03 21:52:00 2014 +0100
@@ -34,7 +34,7 @@
 fun simpset_default thy = the_default (Simpset.get thy);
 
 
-(* diagonstic *)
+(* diagnostic *)
 
 val trace = Attrib.setup_config_bool @{binding "code_simp_trace"} (K false);