Added some changes inspired by Zardosht Kasheff:

- Added a handler call (prepare_index_scan()) to inform storage engines that an index scan is about to take place.
- Extended the maximun key parts for an index from 16 to 32
- Extended MyISAM and Maria engines to support up to 32 parts

Added checks for return value from ha_index_init()



include/my_handler.h:
  Extended number of key parts for MyISAM and Maria from 16 to 32
include/my_pthread.h:
  Ensure we always have 256M of stack.
  (Required to be able to handle the current number of keys and key parts in MyISAM)
mysql-test/r/create.result:
  Extended to test for 32 key parts
mysql-test/r/myisam.result:
  Test that we can create 32 but not 33 key parts
mysql-test/r/ps_1general.result:
  Length of ref is now 2048 as we can have more key parts
mysql-test/r/ps_2myisam.result:
  Length of ref is now 2048 as we can have more key parts
mysql-test/r/ps_3innodb.result:
  Length of ref is now 2048 as we can have more key parts
mysql-test/r/ps_4heap.result:
  Length of ref is now 2048 as we can have more key parts
mysql-test/r/ps_5merge.result:
  Length of ref is now 2048 as we can have more key parts
mysql-test/suite/maria/r/maria.result:
  Max key length is now 1208 bytes
mysql-test/suite/maria/r/maria3.result:
  Max key length is now 1208 bytes
mysql-test/suite/maria/r/ps_maria.result:
  Max key length is now 1208 byte
mysql-test/t/create.test:
  Extended to test for 32 key parts
mysql-test/t/myisam.test:
  Test that we can create 32 but not 33 key parts
sql/handler.cc:
  Check return value from ha_index_init()
sql/handler.h:
  Added a handler call (prepare_index_scan()) to inform storage engines that an index scan is about to take place.
sql/sql_select.cc:
  Checks all return values from ha_index_init()
  Call prepare_index_scan()) to inform storage engines that an index scan is about to take place.
  Fixed indentation
sql/table.cc:
  Fixed wrong types for key_length (rest of code assumed this was 32 bit)
sql/unireg.h:
  Extended the maximun key parts for an index from 16 to 32
storage/maria/ha_maria.cc:
  Don't allocate HA_CHECK on the stack in functions where we call repair() as HA_CHECK is HUGE and will overflow stack
storage/myisam/ha_myisam.cc:
  Don't allocate HA_CHECK on the stack in functions where we call repair() as HA_CHECK is HUGE and will overflow stack
storage/myisam/mi_check.c:
  Fixed wrong check if value overflow
tests/mysql_client_test.c:
  Added fflush() to fix output in case of error
  Fixed wrong check of 'ref' length in EXPLAIN

include/my_pthread.h

@@ -687,15 +687,11 @@ extern void my_mutex_end();
 
 #define THREAD_NAME_SIZE 10
 #ifndef DEFAULT_THREAD_STACK
-#if SIZEOF_CHARP > 4
 /*
-  MySQL can survive with 32K, but some glibc libraries require > 128K stack
-  To resolve hostnames. Also recursive stored procedures needs stack.
+  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)
-#else
-#define DEFAULT_THREAD_STACK	(192*1024)
-#endif
 #endif
 
 #define MY_PTHREAD_LOCK_READ 0