Make prvect tail recursive (fix #9355)

Using a unit test as it's way faster than messing with universes.

You can test with universes by
~~~coq
Set Universe Polymorphism.
Definition x1@{i} := True.
Definition x2 := x1 -> x1.
Definition x3 := x2 -> x2.
Definition x4 := x3 -> x3.
Definition x5 := x4 -> x4.
Definition x6 := x5 -> x5.
Definition x7 := x6 -> x6.
Definition x8 := x7 -> x7.
Definition x9 := x8 -> x8.
Definition x10 := x9 -> x9.
Definition x11 := x10 -> x10.
Definition x12 := x11 -> x11.
Definition x13 := x12 -> x12.
Definition x14 := x13 -> x13.
Definition x15 := x14 -> x14.
Definition x16 := x15 -> x15.
Definition x17 := x16 -> x16.
Definition x18 := x17 -> x17.
Definition x19 := x18 -> x18.

About x19. (* 262144 universes *)
~~~
Note on my machine `About x18.` did not overflow even before this
commit.

0 files changed, 0 insertions, 0 deletions