Php sync method conflict fix

Hi Josh,

Today i noticed that my php files are slow, so i wanted to change `syn sync` from `fromstart` to some minlines. I set `let php_sync_method=200`, which should set `syn sync minlines=200`, but that wasn't the issue. Something was overwriting my php_sync_method to 0. So i found that the default vim plugin for php indenting sets php_sync_method to 0. Exactly in `/usr/share/vim/vim73/indent/php.vim` on line 50, at least on my MacOS, you can see it here also:
https://github.com/2072/PHP-Indenting-for-VIm/blob/master/indent/php.vim#L337

So i came up to idea to rename php_sync_method to php5_sync_method to avoid conflicts and to be able to set manually what we need.