Fix handling of manpage references divided by hyphenation
* lisp/man.el (Man-reference-regexp): Accept a newline as part of a manpage name only if it's preceded by a hyphen. (Bug#34286) (Man-translate-references): Adapt to change in 'Man-reference-regexp'. (Man-default-man-entry): Support references divided between two lines by an ASCII hyphen. This is a left-over from fixing bug#6289.