[RFA 3/3] Document 'set|show exec-file-mismatch (reload|warn|off)'

[Tom Tromey]

Christian> When would someone set this to off, or even warn? I'm wondering is it makes
Christian> sense to add this setting vs always having the reload behavior?

Last time this stuff came up, it turned out there are users who point
gdb at the file with debug symbols while debugging a stripped version on
the target.  IIRC, at the time, build-id and separate debuginfo weren't
widely used, so this was the main way to do this kind of thing.

I don't know if this is still important.  I've only run into trouble
with this behavior, so I welcome the new default at least.

Tom