* lisp/progmodes/f90.el (f90-mode-syntax-table): Use symbol syntax for "_".

* lisp/progmodes/f90.el (f90-mode-syntax-table): Use symbol syntax for "_".
Change all regexps to use things like \_< and \_>.

* lisp/progmodes/ada-mode.el (ada-mode-abbrev-table): Consolidate declaration.
(ada-mode-syntax-table, ada-mode-symbol-syntax-table): Initialize in
the declaration.
(ada-create-syntax-table): Remove.
(ada-capitalize-word): Don't mess with the syntax of "_" since it
already has the right syntax nowadays.
(ada-goto-next-word): Don't change the syntax of "_".

* lisp/progmodes/autoconf.el (autoconf-definition-regexp)
(autoconf-font-lock-keywords, autoconf-current-defun-function):
Handle a _ with symbol syntax.
(autoconf-mode): Don't change the syntax-table for imenu and font-lock.

* lisp/progmodes/vera-mode.el (vera-underscore-is-part-of-word):
* lisp/progmodes/prolog.el (prolog-underscore-wordchar-flag)
(prolog-char-quote-workaround):
* lisp/progmodes/cperl-mode.el (cperl-under-as-char):
* lisp/progmodes/vhdl-mode.el (vhdl-underscore-is-part-of-word):
 Mark as obsolete.
 (vhdl-mode-syntax-table, vhdl-mode-ext-syntax-table): Initialize in
their declaration.
(vhdl-mode-syntax-table-init): Remove.

* lisp/progmodes/ld-script.el (ld-script-mode-syntax-table): Use symbol
syntax for "_".
(ld-script-font-lock-keywords):
Change regexps to use things like \_< and \_>.

* lisp/progmodes/m4-mode.el (m4-mode-syntax-table): Add comment on last change.

* lisp/font-lock.el (lisp-font-lock-keywords-2): Don't highlight obsolete
with-wrapper-hook.

* lisp/mh-e/mh-comp.el (mh-regexp-in-field-p): Minor simplification.