Handle failures from malloc

Most "new" failures fixed in the following files:
- sql_select.cc
- item.cc
- item_func.cc
- opt_subselect.cc

Other things:
- Allocate udf_handler strings in mem_root
  - Required changes in sql_string.h
- Add mem_root as argument to some new [] calls
- Mark udf_handler strings as thread specific
- Removed some comment blocks with code

1 files changed, 2 insertions, 2 deletions

diff --git a/sql/sql_explain.h b/sql/sql_explain.h
index 154769fe289..895c059f1b0 100644
--- a/sql/sql_explain.h
+++ b/sql/sql_explain.h
@@ -589,8 +589,8 @@ public:
     key_name= NULL;
     key_len= (uint)-1;
   }
-  void set(MEM_ROOT *root, KEY *key_name, uint key_len_arg);
-  void set_pseudo_key(MEM_ROOT *root, const char *key_name);
+  bool set(MEM_ROOT *root, KEY *key_name, uint key_len_arg);
+  bool set_pseudo_key(MEM_ROOT *root, const char *key_name);
 
   inline const char *get_key_name() const { return key_name; }
   inline uint get_key_len() const { return key_len; }