Fixed compiler warnings

Fixed compile-pentium64 scripts
Fixed wrong estimate of update_with_key_prefix in sql-bench
Merge bk-internal.mysql.com:/home/bk/mysql-5.1 into mysql.com:/home/my/mysql-5.1
Fixed unsafe define of uint4korr()
Fixed that --extern works with mysql-test-run.pl
Small trivial cleanups
This also fixes a bug in counting number of rows that are updated when we have many simultanous queries
Move all connection handling and command exectuion main loop from sql_parse.cc to sql_connection.cc
Split handle_one_connection() into reusable sub functions.
Split create_new_thread() into reusable sub functions.
Added thread_scheduler; Preliminary interface code for future thread_handling code.

Use 'my_thread_id' for internal thread id's
Make thr_alarm_kill() to depend on thread_id instead of thread
Make thr_abort_locks_for_thread() depend on thread_id instead of thread
In store_globals(), set my_thread_var->id to be thd->thread_id.
Use my_thread_var->id as basis for my_thread_name()
The above changes makes the connection we have between THD and threads more soft.

Added a lot of DBUG_PRINT() and DBUG_ASSERT() functions
Fixed compiler warnings
Fixed core dumps when running with --debug
Removed setting of signal masks (was never used)
Made event code call pthread_exit() (portability fix)
Fixed that event code doesn't call DBUG_xxx functions before my_thread_init() is called.
Made handling of thread_id and thd->variables.pseudo_thread_id uniform.
Removed one common 'not freed memory' warning from mysqltest
Fixed a couple of usage of not initialized warnings (unlikely cases)
Suppress compiler warnings from bdb and (for the moment) warnings from ndb

mysys/mf_keycache.c

@@ -159,8 +159,10 @@ static void unlink_from_queue(KEYCACHE_WQUEUE *wqueue,
                                      struct st_my_thread_var *thread);
 #endif
 static void free_block(KEY_CACHE *keycache, BLOCK_LINK *block);
+#ifndef DBUG_OFF
 static void test_key_cache(KEY_CACHE *keycache,
                            const char *where, my_bool lock);
+#endif
 
 #define KEYCACHE_HASH(f, pos)                                                 \
 (((ulong) ((pos) >> keycache->key_cache_shift)+                               \
@@ -2608,7 +2610,8 @@ static int flush_all_key_blocks(KEY_CACHE *keycache)
     0 on success (always because it can't fail)
 */
 
-int reset_key_cache_counters(const char *name, KEY_CACHE *key_cache)
+int reset_key_cache_counters(const char *name __attribute__((unused)),
+                             KEY_CACHE *key_cache)
 {
   DBUG_ENTER("reset_key_cache_counters");
   if (!key_cache->key_cache_inited)