Use idn_to_ascii function instead of idna_convert library

The `idna_convert` library is outdated and there is now a native PHP function to convert IDNs to Punycode.
It requires `intl` extension or a [polyfill](https://github.com/symfony/polyfill-intl-idn).

`compress_parse_url` will append `?` and `#` to the URI even if there is no query string or hash fragment, and insert `//` even when there is no authority part. To avoid this and the breakage of tests this would cause, let’s call the function only for files having a non-empty authority part of the URI (i.e. non-local files) that contains characters that are not considered printable ASCII (such as bytes of UTF-8 encoded Unicode characters).

In the future, we might leave the IDN support to HTTP library to deal with.

CHANGELOG.md

@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - PHP 7.2 or newer is now required by @Art4 in [#743](https://github.com/simplepie/simplepie/pull/743)
 - Parse\Date: Clean up regex structure by @jtojnar in [#765](https://github.com/simplepie/simplepie/pull/765)
 - Declare strict_types=1 in every file by @Art4 in [#763](https://github.com/simplepie/simplepie/pull/763)
+- Use `idn_to_ascii` function instead of `idna_convert` library (requires `intl` extension or a [polyfill](https://github.com/symfony/polyfill-intl-idn)) by @jtojnar in [#785](https://github.com/simplepie/simplepie/pull/785)
 
 ### Fixed
 

README.markdown

@@ -14,6 +14,7 @@ Requirements
 * PHP 7.2+ (Required since SimplePie 1.8.0)
 * libxml2 (certain 2.7.x releases are too buggy for words, and will crash)
 * One of iconv, mbstring or intl extensions
+* intl extension or [symfony/polyfill-intl-idn](https://github.com/symfony/polyfill-intl-idn) to support IDNs
 * cURL or fsockopen()
 * PCRE support
 
@@ -29,10 +30,8 @@ What comes in the package?
    server for required settings.
 6. `demo/` - A basic feed reader demo that shows off some of SimplePie's more
    noticeable features.
-7. `idn/` - A third-party library that SimplePie can optionally use to
-   understand Internationalized Domain Names (IDNs).
-8. `build/` - Scripts related to generating pieces of SimplePie
-9. `test/` - SimplePie's unit test suite.
+7. `build/` - Scripts related to generating pieces of SimplePie
+8. `test/` - SimplePie's unit test suite.
 
 ### Where's `simplepie.inc`?
 Since SimplePie 1.3, we've split the classes into separate files to make it easier

demo/index.php

@@ -6,7 +6,6 @@
 // Include SimplePie
 // Located in the parent directory
 include_once('../autoloader.php');
-include_once('../idn/idna_convert.class.php');
 
 // Create a new instance of the SimplePie object
 $feed = new \SimplePie\SimplePie();

demo/test.php

@@ -1,6 +1,5 @@
 <?php
 include_once('../autoloader.php');
-include_once('../idn/idna_convert.class.php');
 
 // Parse it
 $feed = new \SimplePie\SimplePie();