Fix Flymake's user-visible accessors of diagnostic positions

Diagnostics are supported by overlays, and they can legitimately move
around.  So flymake-diagnostic-beg and flymake-diagnostic-end must
look up the overlay positions, not the immutable slots of the
flymake--diag structure, which become stale.

* lisp/progmodes/flymake.el (version): Bump to 1.0.8.
(flymake-diagnostic-beg, flymake-diagnostic-end): Use diag's
overlay.
(flymake-show-diagnostic): Use flymake-diagnostic-end,
flymake-diagnostic-beg.
1 job for master in 51 minutes and 42 seconds
Status Job ID Name Coverage
  Test
failed #2363
test-all

00:51:42

 
Name Stage Failure
failed
test-all Test
Makefile:318: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1