Reference language items are out of date

[mdinger]

Reference language items are out of date. The items are listed here. Currently missing these:

slice
slice_mut
panic_bounds_check
panic_fmt
managed_bound

[Diggsey]

There are some other differences too.

• Only present in the code:

opaque
non_zero
range
range_from
range_to
full_range

• Only present in the reference:

strdup_uniq
begin_unwind
closure_exchange_malloc
fail_bounds_check
gc
malloc
free

(presumably panic_bounds_check used to be called fail_bounds_check)