When using ffap-other-window, don't change the window configuration
unless a new buffer has actually been created (Bug#25352).
* lisp/ffap.el (ffap-other-frame): Don't change the window
configuration if no new buffer has been created.
* test/lisp/ffap-tests.el (ffap-other-window--bug-25352): Add unit
test.
* lisp/ffap.el (ffap-gopher-regexp): Only match the KEY part. Note
setting to nil is now supported.
(ffap--gopher-var-on-line): New function.
(ffap-gopher-at-point): Use it instead of the old ffap-gopher-regexp
which could overflow the regexp stack on long lines (Bug#25391). Use
`let-alist' instead of calling `set' on local variables.
* test/lisp/ffap-tests.el (ffap-gopher-at-point): New test.
Prevents that 'ffap-guesser' waste time checking large strings
which are likely not valid candidates (Bug#25243).
* lisp/ffap.el (ffap-max-region-length): New variable.
(ffap-string-at-point): Use it.
* test/lisp/ffap-tests.el: New test suite.
(ffap-tests-25243): Add test for this bug.