Limit join_buffer_size, sort_buffer_size and myisam_sort_buffer_size to 4GB on...

Limit join_buffer_size, sort_buffer_size and myisam_sort_buffer_size to 4GB on all platforms, since the related code in 5.0 is not 64-bit safe. This is patch is a part of work on bug #5731 and will be null-merged to 5.1.

sql/mysqld.cc

@@ -5829,7 +5829,7 @@ log and this option does nothing anymore.",
    "The size of the buffer that is used for full joins.",
    (gptr*) &global_system_variables.join_buff_size,
    (gptr*) &max_system_variables.join_buff_size, 0, GET_ULONG,
-   REQUIRED_ARG, 128*1024L, IO_SIZE*2+MALLOC_OVERHEAD, ~0L, MALLOC_OVERHEAD,
+   REQUIRED_ARG, 128*1024L, IO_SIZE*2+MALLOC_OVERHEAD, UINT_MAX32, MALLOC_OVERHEAD,
    IO_SIZE, 0},
   {"keep_files_on_create", OPT_KEEP_FILES_ON_CREATE,
    "Don't overwrite stale .MYD and .MYI even if no directory is specified.",
@@ -5998,7 +5998,7 @@ The minimum value for this variable is 4096.",
    "The buffer that is allocated when sorting the index when doing a REPAIR or when creating indexes with CREATE INDEX or ALTER TABLE.",
    (gptr*) &global_system_variables.myisam_sort_buff_size,
    (gptr*) &max_system_variables.myisam_sort_buff_size, 0,
-   GET_ULONG, REQUIRED_ARG, 8192*1024, 4, ~0L, 0, 1, 0},
+   GET_ULONG, REQUIRED_ARG, 8192*1024, 4, UINT_MAX32, 0, 1, 0},
   {"myisam_stats_method", OPT_MYISAM_STATS_METHOD,
    "Specifies how MyISAM index statistics collection code should threat NULLs. "
    "Possible values of name are \"nulls_unequal\" (default behavior for 4.1/5.0), "
@@ -6144,7 +6144,7 @@ The minimum value for this variable is 4096.",
    "Each thread that needs to do a sort allocates a buffer of this size.",
    (gptr*) &global_system_variables.sortbuff_size,
    (gptr*) &max_system_variables.sortbuff_size, 0, GET_ULONG, REQUIRED_ARG,
-   MAX_SORT_MEMORY, MIN_SORT_MEMORY+MALLOC_OVERHEAD*2, ~0L, MALLOC_OVERHEAD,
+   MAX_SORT_MEMORY, MIN_SORT_MEMORY+MALLOC_OVERHEAD*2, UINT_MAX32, MALLOC_OVERHEAD,
    1, 0},
 #ifdef HAVE_BERKELEY_DB
   {"sync-bdb-logs", OPT_BDB_SYNC,