PHP Mode for Emacs Code

(php-font-lock-keywords-1, php-font-lock-keywords-2): Add [^_$] to
beginning and [^_] to end of font-lock regular expressions to
avoid false matches in user variable and function names. Affects
highlighting of self, parent, print, break, case, continue, other
keywords and internal constants.

Add missing paren from last commit.

(php-mode-modified): Use a string literal rather than a computed
value.

(php-tags, php-tags-key): Move definition to above
php-mode to avoid byte compiler warning. Use eval-when-compile
for regexp-opt.
(php-font-lock-keywords-1): Use font-lock-preprocessor-face for
PHP and ASP tags.

(php-mode): Overwrite C-style macros rule to recognize PHP tags
instead.
(php-tags, php-tags-key): New constants.
(php-font-lock-keywords-1): Use php-tags-key for syntax
highlighting of PHP tags.

(php-mode): Add commented-out c-lang-defvar statements below
commented-out c-lang-defconst.

(php-mode): Turn on necessary c-mode features with c-add-language,
like c-symbol-key.

(php-mode-modified): Resolve setting constant by
using format-time-string, but still using eval-when-compile.

ChangeLog entries for recent commits.

Use correct regular expression.