SQLite: build with SQLITE_USE_URI=1

[tschoonj]

We have seen some problems attaching to in-memory databases from RSQLite that have been created from within C code, resulting in files being created on the filesystem such as tests/testthat/file:name?mode=memory&vfs=some-stub, due to RSQLite not understanding that these are URIs.

We have managed to resolve these problems with the attached patch, which essentially enables URI support at compile-time.

It may be relevant to reviewers to note that the SQLite developers state that it is safe for most applications to enable URI processing:

Since SQLite always interprets any filename that does not begin with "file:" as an ordinary filename regardless of the URI setting, and because it is very unusual to have an actual file begin with "file:", it is safe for most applications to enable URI processing even if URI filenames are not currently being used.

CC: @jrandall

[krlmlr]

Thanks!

[tschoonj]

Thanks!!