[development] Testing SQLite on Linux

[John Morahan]

This may be obvious, but if you place the database file on a tmpfs, it
runs much faster.  You can do this by specifying e.g. /dev/shm/drupal as
the database name when you install.  Pointless for a real site, of
course, but useful for a once-off local install to run the simpletests.

On my laptop (which admittedly runs dm-crypt, perhaps putting the HD at
an unfair disadvantage) the difference is on the scale of under 17
minutes versus over two hours for running the full test suite.

Just a heads up in case anyone else didn't realize this.

-john