v1.21.3 - Performance improvement for large files

This version includes both PHP syntax support enhancements and performance improvements. See https://github.com/emacs-php/php-mode/projects/1 for all issues for this release. Also, @mallt has helped me improve it with a number of issues. thank you very much.

Added

• Added new Faces to display PHP syntax
  • php-constant-assign
  • php-magical-constant
  • php-errorcontrol-op
• Some funtions have been split into features such as php.el, php-face.el and php-mode-debug.el.

Fixed

• Improved performance when opening large files (#491, #531)

Changed

• Syntax highlighting has been adjusted

Removed

• php-ext and Skeleton templates have been split into php-skeleton (#534)