This PR adds basic support for eta-reduction to `grind`.
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Co-authored-by: Kim Morrison <kim@tqft.net>
Co-authored-by: Kim Morrison <scott.morrison@gmail.com>
This PR adds the attribute `[grind ext]`. It is used to select which
`[ext]` theorems should be used by `grind`. The option `grind +extAll`
instructs `grind` to use all `[ext]` theorems available in the
environment.
After update stage0, we need to add the builtin `[grind ext]`
annotations to key theorems such as `funext`.
