1. Introduce parse_sql() as a high-level replacement for MYSQLparse().
parse_sql() is responsible to switch and restore "parser context"
(THD::m_lip for now).

2. Fix typo in sp.cc: THD::spcont should be reset *before* calling
the parser.


sql/event_data_objects.cc:
  Use parse_sql() instead of MYSQLparse().
sql/mysql_priv.h:
  Introduce parse_sql() instead of auto-generated MYSQLparse.
sql/sp.cc:
  1. Use parse_sql() instead of MYSQLparse().
  2. THD::spcont should be reset before calling the parser.
sql/sql_class.cc:
  Reset THD::m_lip.
sql/sql_parse.cc:
  1. Introduce parse_sql() instead of auto-generated MYSQLparse().
  2. Backup, switch and restore THD::m_lip inside parse_sql().
  3. Use parse_sql() instead of MYSQLparse().
sql/sql_partition.cc:
  Use parse_sql() instead of MYSQLparse().
sql/sql_prepare.cc:
  Use parse_sql() instead of MYSQLparse().
sql/sql_trigger.cc:
  Use parse_sql() instead of MYSQLparse().
sql/sql_view.cc:
  Use parse_sql() instead of MYSQLparse().