xShadowName method is added to the sqlite3_module object and is used
to identify potential shadow tables. The SQLITE_PREPARE_SHADOW argument
to sqlite3_prepare_v3() is defined. It is designed to permit writing to
shadow tables, but is currently an unused placeholder.
FossilOrigin-Name: 31942b3dd3f66eb0d9977bf1cadc2f2d7be7967cce2b55784be0b939dfef1985