asan detects stack-buffer-overflow when using try/catch

[mgaunard]

catch_all_gen is holding the "try" sub-expression by reference, which of course is not valid.
Holding them by value and using base_type instead of that_type fixes the bug.

while, do/while and switch also have this bug.
Interestingly 'if' and 'for' do not.

is_actor appears to also not be consistently specialized.

[djowel]

Will you do a PR for this?

[mgaunard]

#94

[djowel]

#94

Wonderful! Many thanks!