Fix haddock validate problem.

compiler/stgSyn/StgSyn.lhs

@@ -354,12 +354,12 @@ And so the code for let(rec)-things:
   | StgLetNoEscape                  -- remember: ``advanced stuff''
         (GenStgLiveVars occ)        -- Live in the whole let-expression
                                     -- Mustn't overwrite these stack slots
-                                    -- *Doesn't* include binders of the let(rec).
+                                    -- _Doesn't_ include binders of the let(rec).
 
         (GenStgLiveVars occ)        -- Live in the right hand sides (only)
                                     -- These are the ones which must be saved on
                                     -- the stack if they aren't there already
-                                    -- *Does* include binders of the let(rec) if recursive.
+                                    -- _Does_ include binders of the let(rec) if recursive.
 
         (GenStgBinding bndr occ)    -- right hand sides (see below)
         (GenStgExpr bndr occ)       -- body