bug#13795: 24.3.50; epa-insert-keys improvements

[Richard Stallman]

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[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > Are you still seeing this issue in more recent versions of Emacs?

I am running master from June.  epa-insert-keys just took 6 seconds
to insert 700 keys.  I still have a build of master from Oct 2019;
epa-insert-keys took the same time in that version.

I don't remember when I reported this problem or with which Emacs
version, or how long the operation took.

Maybe that conversion job could not be done faster, but epa could save
the resulting text.  That would make it very fast if the keyring is
unchanged.

It could save the text in a file, and compare that file's mtime with
that of the keyring to see whether to regenerate the file.  That way,
the memoization will work from one Emacs session to another.

-- 
Dr Richard Stallman
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)