NpgsqlSchema: Use InvariantCulture on all return DataTables with schema data. This matches what MS' SqlClient does. This matters e.g. on Turkish culture where 'i' is not lower case for 'I'.
Removed unneeded NUnit references in unit tests

NUnit.Core, NUnit.Core.Interfaces, NUnit.Util, was causing build build
errors
Corrected unit test project references

NpgsqlTests2010 now references Npgsql2010 instead of Npgsql2008
Conn can be closed in TransactionScope without prepared transaction

Previously closing a connection within a TransactionScope triggered an
automatic promotion to a prepared transaction. Since by default Postgres
disables these, this made the TransactionScope unusable for many cases.
This is reproduced in
SystemTransactionTests.SimpleTransactionScopeWithImplicitEnlist, which was
failing in stock Postgres installations.

Instead of promoting, we now postpone the close until the (local)
transaction is terminated, i.e. until the TransactionScope ends.
Removed connection leak detection and handling

By Francisco's request
Merge pull request #1 from oskarb/schema-invariant-culture

NpgsqlSchema: Use InvariantCulture on all return DataTables with schema ...
Merge pull request #8 from roji/scope_without_prepared_transactions

Scope without prepared transactions
Sync code with cvs main repository.