This patch adds a `mozIStorageConnection::defaultTransactionType`
attribute that controls the default transaction behavior for the
connection. As before, `mozStorageTransaction` can override the default
behavior for individual transactions.
MozReview-Commit-ID: IRSlMesETWN
Introduce a new SpinningSynchronousClose API that allows to synchronously close
a connection that executed asynchronous statements, by spinning the events loop.
This is expected to be used rarely in particular cases like database corruption.
It is currently [noscript] since the only consumer is cpp, in the future we can
evaluate removing that, if we find more uses for it.
MozReview-Commit-ID: 7SPqutoF9jJ
