Prevent bugs by making DBUG_* expressions syntactically equivalent

to a single statement.
---
Bug#24795: SHOW PROFILE

Profiling is only partially functional on some architectures.  Where 
there is no getrusage() system call, presently Null values are 
returned where it would be required.  Notably, Windows needs some love 
applied to make it as useful.

  Syntax this adds:
  
  SHOW PROFILES
  
  SHOW PROFILE [types] [FOR QUERY n] [OFFSET n] [LIMIT n]
   where "n" is an integer
   and "types" is zero or many (comma-separated) of
      "CPU"
      "MEMORY" (not presently supported)
      "BLOCK IO"
      "CONTEXT SWITCHES"
      "PAGE FAULTS"
      "IPC"
      "SWAPS"
      "SOURCE"
      "ALL"

It also adds a session variable (boolean) "profiling", set to "no"
by default, and (integer) profiling_history_size, set to 15 by 
default.

This patch abstracts setting THDs' "proc_info" behind a macro that 
can be used as a hook into the profiling code when profiling 
support is compiled in.  All future code in this line should use
that mechanism for setting thd->proc_info.

---

Tests are now set to omit the statistics.

---

Adds an Information_schema table, "profiling" for access to 
"show profile" data.
---
Merge zippy.cornsilk.net:/home/cmiller/work/mysql/mysql-5.0-community-3--bug24795
into  zippy.cornsilk.net:/home/cmiller/work/mysql/mysql-5.0-community
---
Fix merge problems.
---
Fixed one bug in the query_source being NULL.  

Updated test results.
---
Include more thorough profiling tests.

Improve support for prepared statements.

Use session-specific query IDs, starting at zero.
---
Selecting from I_S.profiling is no longer quashed in profiling, as
requested by Giuseppe.

Limit the size of captured query text.

No longer log queries that are zero length.

sql/sql_class.h

@@ -521,6 +521,7 @@ struct system_variables
   ulong optimizer_prune_level;
   ulong optimizer_search_depth;
   ulong preload_buff_size;
+  ulong profiling_history_size;
   ulong query_cache_type;
   ulong read_buff_size;
   ulong read_rnd_buff_size;
@@ -1154,6 +1155,9 @@ public:
     Points to info-string that we show in SHOW PROCESSLIST
     You are supposed to update thd->proc_info only if you have coded
     a time-consuming piece that MySQL can get stuck in for a long time.
+
+    Set it using the  thd_proc_info(THD *thread, const char *message)
+    macro/function.
   */
   const char *proc_info;
 
@@ -1308,8 +1312,9 @@ public:
   List	     <MYSQL_ERROR> warn_list;
   uint	     warn_count[(uint) MYSQL_ERROR::WARN_LEVEL_END];
   uint	     total_warn_count;
-  
+#ifdef ENABLED_PROFILING
   PROFILING  profiling;
+#endif
 
   /*
     Id of current query. Statement can be reused to execute several queries