Make innodb_flush_log_at_trx_commit a settable global variable.


innobase/include/srv0srv.h:
  Change the type of srv_flush_log_at_trx_commit.
innobase/srv/srv0srv.c:
  Change the type of srv_flush_log_at_trx_commit.
sql/ha_innodb.cc:
  Remove innobase_flush_log_at_trx_commit.
   (Set srv_flush_log_at_trx_commit directly).
sql/ha_innodb.h:
  Remove innobase_flush_log_at_trx_commit.
   (Set srv_flush_log_at_trx_commit directly).
sql/mysqld.cc:
  Bypass the variable innobase innobase_flush_log_at_trx_commit.
sql/set_var.cc:
  Make innodb_flush_log_at_trx_commit a settable global variable.