bug#61504: 29.0.60; executing byte-code from previous build causes SIGSEGV crash

[Gregory Heytings]

> There seems to be a byte-code change between versions 
> 0ec0a610ed226419269f519021cbe8fb2dde2ed5 (old) and 
> a4aa32bdfff7aaf54efbacbb04b7f2b52fef92a7 (new) which causes the new 
> version to crash with SIGSEGV when executing certain code from an .elc 
> built using the old version. Recompiling the file with the new version 
> causes the new .elc to work correctly.

The bytecode did not change, but the byte codes generated by the 
save-restriction form did change.

Now that I think of it again, it is possible make that change while 
preserving backward compatibility.

Eli, what do you think of the attached patch?  It restores the 'unbind 1' 
at the end of save-restriction, and puts the two data elements into a cons 
instead of pushing them separately.  (Of course this passes make and make 
check, with and without native compilation.)

Improve-backward-compatibility-of-save-restriction.patch
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