prepared statements in embedded library


include/mysql_com.h:
  to make net_flush() working in expressions
libmysqld/lib_sql.cc:
  some bugs fixed
libmysqld/libmysqld.c:
  we already have the define in client_settings.h
sql/protocol.cc:
  net_store_data should work that way in Protocol_prep (embedded server)
sql/protocol.h:
  definition for net_store_data
sql/sql_prepare.cc:
  now it works in embedded library