The code assumed that the number of `Local` and number of locals is the
same thing. In reality though it is not. `Local` actually represents a
group of locals with the same type. The group can declare more than one
variable and the number of them is returned by `Local::count`.
In this PR we acknowledge this fact. Along the way we add a checked
arithmetic for locals_count and max_stack_height summation.
Previously, functions that appear in multiple places
(exported, start function, table) would generate a thunk
for each place they appear in. Those additional thunks are
identical and only only one of them would be referenced.
Main offender are tables with redundant entries.
This commit eliminates those duplicate thunks without adding
any additional overhead.
Sergey Shulepov