PHP Mode for Emacs Code

Tagging the release of php-mode

Update modification date in the header and add
ChangeLog entry for new version.
(php-mode-version-number, php-mode-modified): Mark as 1.5.0
release with today's date.

(php-class-key): Use c-lang-const to retrieve value
for c-symbol-key.
(php-mode): Add underscore (_) to syntax table for
font-lock-defaults.
(php-font-lock-keywords-1, php-font-lock-keywords-2)
(php-font-lock-keywords-3): Change references to \\s_ in regular
expressions to just using \\sw. Remove usage of "[^_$]?" and
"[^_]?" regular expression.

Fix various typos and documentation
string errors. Make in-line comment style consistent.

Fix indentation levels.

Convert tabs to spaces. Add form feed characters between sections.

Removed items in the ChangeLog section. A
ChangeLog file is now included with the source package.
(php-default-face, font-lock-keyword-face)
(font-lock-constant-face): Remove conditional bindings and XEmacs
code that likely does nothing.

(php-imenu-generic-expression): Reverse order of
expression, since Imenu displays it in reverse.
(php-completion-table): Move next to php-complete-function.

Update modification date and add David House to contributor list.

(php-font-lock-keywords-1)
(php-font-lock-keywords-2): Fix regular expression for
highlighting various keywords when they're at the beginning or end
of the line.