Changed default thread stack to 288K to get better memory missalignment...

Changed default thread stack to 288K to get better memory missalignment between stacks of different threads (should speed up things) and to get a bit extra safety.
In maria_open(), don't allocate big arrays on stack as this may lead to stack overflow.
This fixes a valgrind warning detected by buildbot

include/my_pthread.h:
  Changed default thread stack to 288K to get better memory missalignment between stacks of different threads (should speed up things) and to get a bit extra safety.
storage/maria/ma_open.c:
  In maria_open(), don't allocate big arrays on stack as this may lead to stack overflow.

include/my_pthread.h

@@ -691,7 +691,7 @@ extern void my_mutex_end();
   We need to have at least 256K stack to handle calls to myisamchk_init()
   with the current number of keys and key parts.
 */
-#define DEFAULT_THREAD_STACK	(256*1024L)
+#define DEFAULT_THREAD_STACK	(288*1024L)
 #endif
 
 #define MY_PTHREAD_LOCK_READ 0

storage/maria/ma_open.c

@@ -256,15 +256,16 @@ MARIA_HA *maria_clone(MARIA_SHARE *share, int mode)
 MARIA_HA *maria_open(const char *name, int mode, uint open_flags)
 {
   int kfile,open_mode,save_errno;
-  uint i,j,len,errpos,head_length,base_pos,info_length,keys, realpath_err,
+  uint i,j,len,errpos,head_length,base_pos,keys, realpath_err,
     key_parts,unique_key_parts,fulltext_keys,uniques;
+  size_t info_length;
   char name_buff[FN_REFLEN], org_name[FN_REFLEN], index_name[FN_REFLEN],
        data_name[FN_REFLEN];
   uchar *disk_cache, *disk_pos, *end_pos;
   MARIA_HA info,*m_info,*old_info;
   MARIA_SHARE share_buff,*share;
-  double rec_per_key_part[HA_MAX_POSSIBLE_KEY*HA_MAX_KEY_SEG];
-  ulong  nulls_per_key_part[HA_MAX_POSSIBLE_KEY*HA_MAX_KEY_SEG];
+  double *rec_per_key_part;
+  ulong  *nulls_per_key_part;
   my_off_t key_root[HA_MAX_POSSIBLE_KEY];
   ulonglong max_key_file_length, max_data_file_length;
   my_bool versioning= 1;
@@ -294,8 +295,6 @@ MARIA_HA *maria_open(const char *name, int mode, uint open_flags)
   {
     share= &share_buff;
     bzero((uchar*) &share_buff,sizeof(share_buff));
-    share_buff.state.rec_per_key_part=   rec_per_key_part;
-    share_buff.state.nulls_per_key_part= nulls_per_key_part;
     share_buff.state.key_root=key_root;
     share_buff.pagecache= multi_pagecache_search((uchar*) name_buff,
 						 (uint) strlen(name_buff),
@@ -360,11 +359,27 @@ MARIA_HA *maria_open(const char *name, int mode, uint open_flags)
 
     info_length=mi_uint2korr(share->state.header.header_length);
     base_pos= mi_uint2korr(share->state.header.base_pos);
-    if (!(disk_cache= (uchar*) my_alloca(info_length+128)))
+
+    /*
+      Allocate space for header information and for data that is too
+      big to keep on stack
+    */
+    if (!my_multi_malloc(MY_WME,
+                         &disk_cache, info_length+128,
+                         &rec_per_key_part,
+                         (sizeof(*rec_per_key_part) * HA_MAX_POSSIBLE_KEY *
+                          HA_MAX_KEY_SEG),
+                         &nulls_per_key_part,
+                         (sizeof(*nulls_per_key_part) * HA_MAX_POSSIBLE_KEY *
+                          HA_MAX_KEY_SEG),
+                         NullS))
     {
       my_errno=ENOMEM;
       goto err;
     }
+    share_buff.state.rec_per_key_part=   rec_per_key_part;
+    share_buff.state.nulls_per_key_part= nulls_per_key_part;
+
     end_pos=disk_cache+info_length;
     errpos= 3;
     if (my_pread(kfile, disk_cache, info_length, 0L, MYF(MY_NABP)))
@@ -783,7 +798,7 @@ MARIA_HA *maria_open(const char *name, int mode, uint open_flags)
 					(keys ? MARIA_INDEX_BLOCK_MARGIN *
 					 share->block_size * keys : 0));
     share->block_size= share->base.block_size;
-    my_afree(disk_cache);
+    my_free(disk_cache, MYF(0));
     _ma_setup_functions(share);
     if ((*share->once_init)(share, info.dfile.file))
       goto err;
@@ -926,9 +941,7 @@ MARIA_HA *maria_open(const char *name, int mode, uint open_flags)
     my_free(share,MYF(0));
     /* fall through */
   case 3:
-    /* fall through */
-  case 2:
-    my_afree(disk_cache);
+    my_free(disk_cache, MYF(0));
     /* fall through */
   case 1:
     VOID(my_close(kfile,MYF(0)));