(hs-show-all, hs-safety-is-job-n): Fix messages.

(hs-show-all, hs-safety-is-job-n): Fix messages.

Changed to use overlays for hiding instead of selective display.
Commented out the support for XEmacs because it doesn't support overlays.
(hs-special-modes-alist): Added support for java-mode.
(hs-minor-mode-hook): New variable.
(hs-c-start-regexp, hs-c-end-regexp, hs-forward-sexp-func)
(hs-block-start-regexp, hs-block-end-regexp)
(hs-find-block-beginning): Doc string fixes.
(hs-hide-comments-when-hiding-all): New variable.
(hs-safety-is-job-n, hs-minor-mode, hs-flag-region):
Use overlays for hiding.
(hs-inside-single-line-comment-p, hs-discard-overlays)
(hs-already-hidden-p): New internal functions.
(hs-hide-block-at-point, hs-hide-initial-comment-block)
(java-hs-forward-sexp, hs-mouse-toggle-hiding): New functions.
(hs-inside-comment-p, hs-hide-block)
(hs-show-block): Added support for single line comments.
(hs-hide-all): Added support for hiding comments.