sql_lex.yy / sql_yacc_ora.yy refactoring for MDEV-10411.

1. Adding const qualifiers into a few method parameters.

2. Adding methods:
- sp_label::block_label_declare()
- LEX::sp_block_init()
- LEX::sp_block_finalize()
  to share more code between the files sql_yacc.yy and sql_yacc_ora.yy,
  as well as between the rules sp_labeled_block, sp_unlabeled_block,
  sp_unlabeled_block_not_atomic.

3. sql_yacc.yy, sql_yacc_ora.yy changes:
- Removing sp_block_content
- Reorganizing the grammar so the rules sp_labeled_block,
  sp_unlabeled_block, sp_unlabeled_block_not_atomic now
  contain both BEGIN_SYM and END keywords. Previously,
  BEGIN_SYM and END resided in different rules.
  This change makes the grammar easier to read,
  as well as simplifies adding Oracle-style DECLARE section (coming soon):
    DECLARE
      ..
    BEGIN
      ..
    END;

  Good side effects:
  - SP block related grammar does not use Lex->name any more.
  - The "splabel" member was removed from %union

1 files changed, 15 insertions, 3 deletions

diff --git a/sql/sp_pcontext.h b/sql/sp_pcontext.h
index 1ef99219e8e..cbebc157dbb 100644
--- a/sql/sp_pcontext.h
+++ b/sql/sp_pcontext.h
@@ -108,7 +108,8 @@ public:
   class sp_pcontext *ctx;
 
 public:
-  sp_label(LEX_STRING _name, uint _ip, enum_type _type, sp_pcontext *_ctx)
+  sp_label(const LEX_STRING _name,
+           uint _ip, enum_type _type, sp_pcontext *_ctx)
    :Sql_alloc(),
     name(_name),
     ip(_ip),
@@ -401,9 +402,9 @@ public:
   // Labels.
   /////////////////////////////////////////////////////////////////////////
 
-  sp_label *push_label(THD *thd, LEX_STRING name, uint ip);
+  sp_label *push_label(THD *thd, const LEX_STRING name, uint ip);
 
-  sp_label *find_label(LEX_STRING name);
+  sp_label *find_label(const LEX_STRING name);
 
   sp_label *last_label()
   {
@@ -418,6 +419,17 @@ public:
   sp_label *pop_label()
   { return m_labels.pop(); }
 
+  bool block_label_declare(LEX_STRING label)
+  {
+    sp_label *lab= find_label(label);
+    if (lab)
+    {
+      my_error(ER_SP_LABEL_REDEFINE, MYF(0), label.str);
+      return true;
+    }
+    return false;
+  }
+
   /////////////////////////////////////////////////////////////////////////
   // Conditions.
   /////////////////////////////////////////////////////////////////////////