Add a brief comment explaning non-capturing group regexes

Signed-off-by: Simon Deziel <simon@sdeziel.info>

debian/php-cgi.conf

 # This file replaces old system MIME types and sets them only in the
 # Apache webserver
 
+# Using (?:pattern) instead of (pattern) is a small optimization that
+# avoid capturing the matching pattern (as $1) which isn't used here
 # application/x-httpd-php                        phtml php
 <FilesMatch ".+\.ph(?:ar|p|tml)$">
     SetHandler application/x-httpd-php

debian/php-fpm.conf

@@ -6,6 +6,8 @@
     SetEnvIfNoCase ^Authorization$ "(.+)" HTTP_AUTHORIZATION=$1
     </IfModule>
 
+    # Using (?:pattern) instead of (pattern) is a small optimization that
+    # avoid capturing the matching pattern (as $1) which isn't used here
     <FilesMatch ".+\.ph(?:ar|p|tml)$">
         SetHandler "proxy:unix:/run/php/php@PHP_VERSION@-fpm.sock|fcgi://localhost"
     </FilesMatch>

debian/php.conf

+# Using (?:pattern) instead of (pattern) is a small optimization that
+# avoid capturing the matching pattern (as $1) which isn't used here
 <FilesMatch ".+\.ph(?:ar|p|tml)$">
     SetHandler application/x-httpd-php
 </FilesMatch>