Major rehacking and cleanup of sp_pcontext.

This finishes (almost) WL#2002: Implement stored procedure GOTO.
Only the syntax issue for free labels remains ("label L;" vs "L:").


include/mysqld_error.h:
  New error code for GOTO in SP handler.
mysql-test/r/sp-error.result:
  New error test cases for GOTO.
mysql-test/r/sp.result:
  New test cases for GOTO.
  Also removed some things that made it impossible to run the test in
  an external (debugged) mysqld.
mysql-test/t/sp-error.test:
  New error test cases for GOTO.
mysql-test/t/sp.test:
  New test cases for GOTO.
  Also removed some things that made it impossible to run the test in
  an external (debugged) mysqld.
sql/share/czech/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/danish/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/dutch/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/english/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/estonian/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/french/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/german/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/greek/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/hungarian/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/italian/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/japanese/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/korean/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/norwegian-ny/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/norwegian/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/polish/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/portuguese/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/romanian/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/russian/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/serbian/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/slovak/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/spanish/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/swedish/errmsg.txt:
  New error message for GOTO in SP handler.
sql/share/ukrainian/errmsg.txt:
  New error message for GOTO in SP handler.
sql/sp_head.cc:
  Code cleanup (renaming of pcontext methods), support goto, and fixed bug
  in jump shortcutting in the optimizer (detect infinite loops).
sql/sp_head.h:
  Code cleanup (renaming of pcontext methods), support goto, and fixed bug
  in jump shortcutting in the optimizer (detect infinite loops).
sql/sp_pcontext.cc:
  Major rehack and cleanup:
  - We now push and pop a chain of contexts during parsing (instead of having
    a single one).
  - Makes error detection for GOTO easier and enables some optmizations and
    debugger support.
  - Makes it a little trickier to keep track on variable and cursor indexes instead.
  - Renamed things to get a more consistent naming scheme too.
sql/sp_pcontext.h:
  Major rehack and cleanup:
  - We now push and pop a chain of contexts during parsing (instead of having
    a single one).
  - Makes error detection for GOTO easier and enables some optmizations and
    debugger support.
  - Makes it a little trickier to keep track on variable and cursor indexes instead.
  - Renamed things to get a more consistent naming scheme too.
sql/sql_yacc.yy:
  Changes to reflect the rework and renamings in sp_pcontext, and fixed
  some GOTO error checking.

sql/share/korean/errmsg.txt

@@ -360,3 +360,4 @@ character-set=euckr
 "View being updated does not have complete key of underlying table in it"
 "View '%-.64s.%-.64s' references invalid table(s) or column(s)"
 "Can't drop a %s from within another stored routine"
+"GOTO is not allowed in a stored procedure handler"