templates and iterators in stacktraces

[timotheecour]

proposal

use a LRU cache with N (=10) most recent template/iterator calls, and upon stacktrace, show those to give more context

rationale

alternative would be to identify all exit points of templates/iterators, which may be doable but is harder to implement (and possibly inefficient)

links

see also nkComesFrom which IIRC had similar goals

[juancarlospaco]

My idea was to add lru usable for stuff like these...