Refactor the SQL parameter processing so that parameter names for values
that are optimized out of the prepare statement are not forgotten.

FossilOrigin-Name: b3aaf715b60b8a338cc6c92dad1ead4a3f7146a3
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index bba0b3c..fd86158 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2230,9 +2230,8 @@
   ** each recursion */
 
   int nVar;            /* Number of '?' variables seen in the SQL so far */
-  int nVarExpr;        /* Number of used slots in apVarExpr[] */
-  int nVarExprAlloc;   /* Number of allocated slots in apVarExpr[] */
-  Expr **apVarExpr;    /* Pointers to :aaa and $aaaa wildcard expressions */
+  int nzVar;           /* Number of available slots in azVar[] */
+  char **azVar;        /* Pointers to names of parameters */
   Vdbe *pReprepare;    /* VM being reprepared (sqlite3Reprepare()) */
   int nAlias;          /* Number of aliased result set columns */
   int nAliasAlloc;     /* Number of allocated slots for aAlias[] */