Provide a ~me Xapian synonym for all of the user's configured email
addresses.
+Add symbol hiding so that we don't risk leaking any private symbols
+into the shared-library interface.
+
+Audit all libnotmuch entry points to ensure that all Xapian calls are
+wrapped in a try/catch block.
+
Search syntax
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Implement support for "tag:*" to expand to all tags.