play around with state function handlers
Move the benchmarks out of de.rs
checkpoint vec without Sep, 184ns vs 182ns
switch back to lookahead, 175ns vs 184ns
Migrate enum bench to lookahead
Optimize away one state in enums
Extend bench_vec tests
minor cleanup
Add Vec<u8> benchmarks
Sep is unused
Inline expect_rest_of_collection
Rewrite to work around rust/issues/11751. 162ns vs 156ns
Minor cleanup
Reenable the tests
Update deserializing hashmaps
reenable struct benchmarks
flesh out struct benchmarks
update to rust HEAD (20a415)

struct decoder: 2417ns
struct deserializer: 1640ns
Simplify the struct deserializer state machine

2515ns vs 3058ns
Replace StructField with Str/String. 2322ns vs 2982ns