Increase the default SQLITE_MAX_SCHEMA_RETRY to 50. Make sure that macro

covers every case where a prepared statement might need to be reprepared due
to a schema change.  The sqlite3_exec() interface now uses 
sqlite3_prepare_v2().

FossilOrigin-Name: c1d7304c80c4a6244c8a9f6fad1eebd0f339c724

src/vdbeapi.c

@@ -453,14 +453,6 @@ end_of_step:
   return (rc&db->errMask);
 }
 
-/*
-** The maximum number of times that a statement will try to reparse
-** itself before giving up and returning SQLITE_SCHEMA.
-*/
-#ifndef SQLITE_MAX_SCHEMA_RETRY
-# define SQLITE_MAX_SCHEMA_RETRY 5
-#endif
-
 /*
 ** This is the top-level implementation of sqlite3_step().  Call
 ** sqlite3Step() to do most of the work.  If a schema error occurs,