Add the SQLITE_DEFAULT_DEFENSIVE compile-time option. Fix up test cases

so that they work with DEFENSIVE enabled.

FossilOrigin-Name: 3212733cb6d1a59516d67a86df7c7b1d2456a1b2e5d7080c26b0e87b2609c65d

test/shared8.test

@@ -62,6 +62,7 @@ do_test 1.0 {
 } {1 i 2 ii 3 iii 4 iv}
 
 do_test 1.1 {
+  sqlite3_db_config db1 DEFENSIVE 0
   execsql { 
     PRAGMA writable_schema = 1;
     DELETE FROM sqlite_master WHERE 1;