e4708260c7
Define keywords for the MLIR syntax. This allows better recognition of
semantic constructs such as SSA value identification e.g. `%foo` which
gives improved motion handling when using 'word based' such as `w, e`.
This is based on the work done for the LLVM IR in
8c46413f34.
Signed-off-by: Jack Frankland <jack.frankland@arm.com>