Ignore "safe" early fatal errors when importing Swift modules.
Ignore "safe" early fatal errors when importing Swift modules.

Some early module import diagnostics do not utterly destroy the Swift
AST context, so add them to the list of ignored diagnostics.

Unbreaks the Swift backwards compatibility tests.

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb