There is one consideration: fil_init() chooses the tablespace hash size
based on the initial value of srv_file_per_table.  However, this is nothing
new: InnoDB could be started with innodb_file_per_table=0 even though
*.ibd files exist.

srv_file_per_table: Declare as my_bool instead of ibool, because
MYSQL_SYSVAR_BOOL() expects a pointer to my_bool.  Document the
variable also in srv0srv.h.

innobase_start_or_create_for_mysql(): Note why it is OK to temporarily
clear srv_file_per_table.

innobase_file_per_table: Remove.