Test #9209 in th/T9209
Fix #9209, by reporting an error instead of panicking on bad splices.
Test #7484 in th/T7484
Fix #7484, checking for good binder names in Convert.

This commit also refactors a bunch of lexeme-oriented code into
a new module Lexeme.
Test #1476 in th/T1476
Test that nested pattern splices don't scope (#1476).

Test case: th/T1476b.
Fix #1476 by making splice patterns work.

Unfortunately, splice patterns in brackets still do not work
because we don't run splices in brackets. Without running a pattern
splice, we can't know what variables it binds, so we're stuck.

This is still a substantial improvement, and it may be the best
we can do. Still must document new behavior.
Release notes for #1476, #7484.
Fix #9220 by adding role annotations.

This includes a submodule update for `array`.
There is also an added test in libraries/array/tests/T9220.
Test #9151 in typecheck/should_compile/T9151.

This test case should pass right now -- the bug is fixed,
presumably by #9200.
Add release notes for #8100, #9527, and #9064.
Test #9318 in typecheck/should_fail/T9318
Test #9201 in typecheck/should_fail/T9201
Update manual to get rid of bogus `coerce` example (#9788)
Test #9109 in typecheck/should_fail/T9109