CLAUSE FAILS OR ABORTS SERVER".
 
Attempt to re-execute prepared ALTER TABLE statement which 
involves .FRM-only changes and also have RENAME clause led
to unwarranted 'Table doesn't exist' error in production
builds and assertion failure for debug builds.
 
This problem stemmed from the fact that for such ALTER TABLE
mysql_alter_table() code changed table list element for table 
to be altered when it tried to re-open table under new name. 
Since this change was not reverted back before next 
re-execution, it made this statement re-execution unsafe.
 
This fix addresses this problem by avoiding changing table list
element from the main table list in such a situation. Instead 
temporary TABLE_LIST object is used.