various known problems, but good enough for a checkpoint commit.


mysql-test/r/sp.result:
  New tests for invoking simple FUNCTIONs.
mysql-test/t/sp.test:
  New tests for invoking simple FUNCTIONs.
sql/item_func.cc:
  New Item_func_sp for stored FUNCTIONs.
sql/item_func.h:
  New Item_func_sp for stored FUNCTIONs.
sql/sp.cc:
  Close mysql.proc table earlier so recursive find_function calls work.
  Added temporary sp_function_exists() function for checking without parsing.
sql/sp.h:
  Added temporary sp_function_exists() function for checking without parsing.
sql/sp_head.cc:
  New code for executing a FUNCTION. (And reworked some of the old code in the process.)
sql/sp_head.h:
  New code for executing a FUNCTION.
sql/sp_rcontext.h:
  Added result slot for FUNCTIONs.
sql/sql_lex.cc:
  Added check for stored FUNCTION, analogous to UDFs.
sql/sql_parse.cc:
  sp_head::execute was renamed into execute_procedure.
sql/sql_yacc.yy:
  Added parsing of stored FUNCTION invocation and code generation for RETURN statement.