for better jump support. Some flow control support added too (but not
complete).


sql/lex.h:
  Added more keywords for embedded SQL.
sql/sp_head.cc:
  Fixed bugs in the parameter evaluation.
  Modified execute() for better jump support.
  Added jump instruction and backpatch support.
sql/sp_head.h:
  Fixed bugs in the parameter evaluation.
  Modified execute() for better jump support.
  Added jump instruction and backpatch support.
sql/sp_pcontext.cc:
  Added label support.
sql/sp_pcontext.h:
  Added label support.
sql/sql_yacc.yy:
  Outlined flow control constructs (parses, but nothing generated yet).