Most parts of the parser can expect that the stack overflow check
in transformExprRecurse() will trigger before things get desperate.
However, transformFromClauseItem() can recurse directly to self
without having analyzed any expressions, so it's possible to drive
it to a stack-overrun crash.  Add a check to prevent that.

Per bug #17583 from Egor Chindyaskin.  Back-patch to all supported
branches.

Richard Guo

Discussion: https://postgr.es/m/17583-33be55b9f981f75c@postgresql.org