Merge from upstream, upto version 5.22.

Merge from upstream, upto version 5.22.
After 5.0:
 `cperl-add-tags-recurse-noxs-fullpath': new function (for -batch mode)

 Fine-grained changelog:
`cperl-hook-after-change':	New configuration variable
`cperl-vc-sccs-header':	Likewise.
`cperl-vc-sccs-header':	Likewise.
`cperl-vc-header-alist':	Default via two preceding variables
`cperl-invalid-face':	Remove double quoting under XEmacs
                                (still needed under 21.2)
`cperl-tips':		Update URLs for resources
`cperl-problems':		Likewise.
`cperl-praise':		Mention new features
New C-c key bindings:	for `cperl-find-bad-style',
`cperl-pod-spell', `cperl-here-doc-spell', `cperl-narrow-to-here-doc',
`cperl-perdoc', `cperl-perldoc-at-point'
CPerl Mode menu changes:	"Fix style by spaces", "Imenu on Perl Info"
moved, new submenu of Tools with Ispell entries and narrowing.
`cperl-after-sub-regexp':	New defsubst
`cperl-imenu--function-name-regexp-perl': Use `cperl-after-sub-regexp',
                        Allows heads up to head4
                        Allow "package;"
`defun-prompt-regexp':	Use `cperl-after-sub-regexp',
`paren-backwards-message':	??? Something for XEmacs???
`cperl-mode':		Never auto-switch abbrev-mode off
                        Try to allow '_' be non-word char
                        Do not use `font-lock-unfontify-region-function' on XEmacs
                        Reset syntax cache on mode start
                        Support multiline facification (even
                                on legacy `font-lock')
`cperl-facemenu-add-face-function':	??? Some contributed code ???
`cperl-after-change-function':	Since `font-lock' and `lazy-lock'
        refuse to inform us whether the fontification is due to lazy
        calling or due to edit to a buffer, install our own hook
        (controlled by `cperl-hook-after-change')
`cperl-electric-pod':	=cut may have been recognized as start
`cperl-block-p':		Moved, updated for attributes
`cperl-calculate-indent':	Try to allow '_' be non-word char
                        Support subs with attributes
`cperl-where-am-i':		Queit (?) a warning
`cperl-cached-syntax-table'	New function
`cperl-forward-re':		Use `cperl-cached-syntax-table'
`cperl-unwind-to-safe':	Recognize `syntax-type' property
                                changing in a middle of line
`cperl-find-sub-attrs':	New function
`cperl-find-pods-heres':	Allow many <<EOP per line
                        Allow subs with attributes
                        Major speedups (3.5x..15x on a real-life
                                test file nph-proxy.pl)
                        Recognize "extproc " (OS/2)
                                case-folded and only at start
                        /x on s///x with empty replacement was
                                not recognized
                        Better comments
`cperl-after-block-p':	Remarks on diff with `cperl-block-p'
                        Allow subs with attributes, labels
                        Do not confuse "else::foo" with "else"
                        Minor optimizations...
`cperl-after-expr-p':	Try to allow '_' be non-word char
`cperl-fill-paragraph':	Try to detect a major bug in Emacs
        with `looking-at' inside `narrow' and bulk out if found
`cperl-imenu--create-perl-index':	Updates for new
        `cperl-imenu--function-name-regexp-perl'
`cperl-outline-level':	Likewise
`cperl-init-faces':		Allow multiline subroutine headers
        and my/our declarations, and ones with comments
                        Allow subroutine attributes
`cperl-imenu-on-info':	Better docstring.
`cperl-etags'		Rudimentary support for attributes
                        Support for packages and "package;"
`cperl-add-tags-recurse-noxs':	Better (?) docstring
`cperl-add-tags-recurse-noxs-fullpath': Likewise
`cperl-tags-hier-init':	Misprint for `fboundp' fixed
`cperl-not-bad-style-regexp':	Try to allow '_' be non-word char
`cperl-perldoc':		Add autoload
`cperl-perldoc-at-point':	Likewise
`cperl-here-doc-spell':	New function
`cperl-pod-spell':		Likewise
`cperl-map-pods-heres':	Likewise
`cperl-get-here-doc-region':	Likewise
`cperl-font-lock-fontify-region-function': Likewise (backward compatibility
                                        for legacy `font-lock')
`cperl-font-lock-unfontify-region-function': Fix style
`cperl-fontify-syntaxically':	Recognize and optimize away
        deferred calls with no-change.  Governed by `cperl-hook-after-change'
`cperl-fontify-update':	Recognize that syntaxification region
        can be larger than fontification one.
        XXXX we leave `cperl-postpone' property, so this is quadratic...
`cperl-fontify-update-bad':	Temporary placeholder until
        it is clear how to implement `cperl-fontify-update'.
`cperl-time-fontification':	New function
`attrib-group':		New text attribute
`multiline':		New value: `syntax-type' text attribute