Permalinks: Detect Caddy web server support.

Support pretty permalinks when Caddy server is detected.

Props swissspidy, mukesh27, sadpencil, cfinnberg, viliamkopecky.
Fixes #41877.
Built from https://develop.svn.wordpress.org/trunk@57612


git-svn-id: http://core.svn.wordpress.org/trunk@57113 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/options-permalink.php

@@ -154,7 +154,7 @@ if ( $iis7_permalinks ) {
 	} else {
 		$writable = false;
 	}
-} elseif ( $is_nginx ) {
+} elseif ( $is_nginx || $is_caddy ) {
 	$writable = false;
 } else {
 	if ( ( ! file_exists( $home_path . '.htaccess' )
@@ -190,7 +190,7 @@ if ( $structure_updated ) {
 					'<code>web.config</code>'
 				);
 			}
-		} elseif ( ! $is_nginx && $htaccess_update_required && ! $writable ) {
+		} elseif ( ! $is_nginx && ! $is_caddy && $htaccess_update_required && ! $writable ) {
 			$message = sprintf(
 				/* translators: %s: .htaccess */
 				__( 'You should update your %s file now.' ),