Some dbapi implementations demand fetchmany() size arg as positional

[J Pellerin]

At least sqlite and mssql using odbc raise exceptions when their cursor.fetchmany() is called with a keyword arg, eg: cursor.fetchmany(size=2).

Attached is a patch including a simple test case for fetchmany and a change to pass the size arg through as positional.

[J Pellerin]

Patch to change fetchmany() to use positional arg, with test case

[Mike Bayer]

changeset:2450