[mi] kill release_value calls

[Vladimir Prus <ghost@cs.msu.su>]

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This patch removes all calls to release_value in varobj.c, except
for one. We only need to call release_value when we're storing
a value for indefinite future use, and install_new_value is the
only such place.  The extra release_value calls either 
are time-consuming no-ops, or lead to memory leaks, 
depending on the value type.

OK?

- Volodya

	* varobj.c (c_value_of_root, c_value_of_child)
	(cplus_value_of_child): Don't call release_value.


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--- gdb/varobj.c	(/mirrors/gdb_mainline)	(revision 3220)
+++ gdb/varobj.c	(/patches/gdb/release_value/gdb_mainline)	(revision 3220)
@@ -1985,13 +1985,8 @@ c_value_of_root (struct varobj **var_han
   if (within_scope)
     {
       /* We need to catch errors here, because if evaluate
-         expression fails we just want to make val->error = 1 and
-         go on */
-      if (gdb_evaluate_expression (var->root->exp, &new_val))
-	{
-	  release_value (new_val);
-	}
-
+         expression fails we want to just return NULL.  */
+      gdb_evaluate_expression (var->root->exp, &new_val);
       return new_val;
     }
 
@@ -2003,8 +1998,6 @@ c_value_of_child (struct varobj *parent,
 {
   struct value *value = NULL;
   c_describe_child (parent, index, NULL, &value, NULL);
-  if (value != NULL)
-    release_value (value);
 
   return value;
 }
@@ -2338,9 +2331,6 @@ cplus_value_of_child (struct varobj *par
 	  name = name_of_child (parent, index);
 	  gdb_value_struct_elt (NULL, &value, &temp, NULL, name, NULL,
 				"cplus_structure");
-	  if (value != NULL)
-	    release_value (value);
-
 	  xfree (name);
 	}
       else if (index >= TYPE_N_BASECLASSES (type))
@@ -2368,7 +2358,6 @@ cplus_value_of_child (struct varobj *par
 	      if (temp != NULL)
 		{
 		  value = value_cast (TYPE_FIELD_TYPE (type, index), temp);
-		  release_value (value);
 		}
 	      else
 		{