bug#27779: 26.0.50: read -- Re-entering top level after C stack overflow

[Keith David Bershatsky]

This is a work in progress, but here is a partial:

The first time I see a break in the prior expected behavior was on 11/19/2017 
(c61ee94959ba96b2a327df0684593f7e569e30be) when portions of Emacs 25 were 
merged with the master branch and `emacs.c` was modified.  Here is a partial 
reversal of the code that broke the ability to avoid a stack overflow by 
setting `ulimit -S -s unlimited`.  The patch applies to the above-mentioned 
head -- i.e., the patch will apply following a hard reset.

I have not yet been able to follow the subsequent breaks to avoid a stack 
overflow with the current master branch.

patch_5e2ae74df54d4090c591c79ab13e7713c6654b9c.diff
Description: application/diff