bug#40000: 27.0.60; next-single-char-property-change hangs on bad argument

[Federico Tedin]

(congratulations on bug #40000! :-)

I'm attaching a patch which solves the issue. Now, all the
`next-*-property-change' functions return LIMIT when it has been
specified and no properties where found up to the buffer's end.

On the other hand, the `previous-*-property-change' functions are a bit
inconsistent for negative values of LIMIT:

(previous-single-char-property-change 2 'test nil -1) -> `args-out-of-range' 
(previous-single-property-change      2 'test nil -1) -> -1
(previous-char-property-change        2           -1) ->  1
(previous-property-change             2       nil -1) -> -1

For positive values of LIMIT I didn't find any problems. Although a
negative value for LIMIT doesn't make any sense, only the documentation
for `previous-char-property-change' mentions that "LIMIT is a no-op if
it is less than (point-min)". So maybe this behavior could be added to
the other 3 functions as well.

0001-Prevent-hanging-in-next-single-char-property-change.patch
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