bug#9824: Info fails to follow multi-line links to manuals with dots

[Juri Linkov]

For example, clicking on the following link fails to navigate to another
Info manual:

  languages, are documented in a separate manual.  *Note Introduction:
  (gccint-4.4)Top.

because a regexp for leading space in `Info-following-node-name-re'
doesn't take into account multi-line case.

Links to manuals without dots in the file name currently work
just by accident, e.g. clicking on:

  are performed by running the function.  *Note What Is a Function:
  (elisp)What Is a Function.

works because the regexp for unallowed chars in node names
doesn't contain parens (but contains dots) and matches everything
including file names (without dots).

This is wrong but I hesitate to make the regexp more restrictive
by disallowing parens in node names because Info currently using
regexp matching extensively is very brittle.

The following patch makes the regexp for leading space more permissive
by allowing newlines in leading space:

=== modified file 'lisp/info.el'
--- lisp/info.el        2011-09-24 19:18:43 +0000
+++ lisp/info.el        2011-10-21 14:10:04 +0000
@@ -2020,7 +2020,7 @@ (defun Info-following-node-name-re (&opt
 Submatch 2 if non-nil is the parenthesized file name part of the node name.
 Submatch 3 is the local part of the node name.
 End of submatch 0, 1, and 3 are the same, so you can safely concat."
-  (concat "[ \t]*"                     ;Skip leading space.
+  (concat "[ \t\n]*"                   ;Skip leading space.
          "\\(\\(([^)]+)\\)?"   ;Node name can start with a file name.
          "\\([" (or allowedchars "^,\t\n") "]*" ;Any number of allowed chars.
          "[" (or allowedchars "^,\t\n") " ]" ;The last char can't be a space.