Introduce a new API for TableAmRoutine

[Japin Li]

Hi, hackers

Recently, I'm trying to implement a new TAM for PostgreSQL, I find there is no
API for handling table's option.  For example:

    CREATE TABLE t (...) USING new_am WITH (...);

Is it possible add a new API to handle table's option in TableAmRoutine?

--
Regrads,
Japin Li.