[php-maint] Bug#571714: maybe put info into comment

[Stefan Fritsch]

Two questions:

- Shouldn't it be php_admin_flag instead of php_admin_value?

- Maybe it would be a good idea to put the info into a comment in the 
config file? AFAIUI, if someone tries the obvious solution to set 
php_admin_flag/value engine on, this would prevent users from setting 
"php_flag engine off" in their .htaccess (but I haven't tested that).