The `phpinfo()` section of the Curl extension lists individual features
supported by the particular ext-Curl + libcurl build. However, the
`curl_version()` function return values do not indicate the same level of
details.
`curl_version()` has a `protocols` key that returns an array of all protocols
supported by the build. But the `features` key is a bitmask of all the features.
Checking the availability of certain feature requires knowing the corresponding
`CURL_VERSION` constant, and checking the availability of the constant and a
bitmask check for it in the `features` value.
For example, to determine HTTP2 support, it requires evaluating:
```php
defined('CURL_VERSION_HTTP2') && (curl_version()['features'] & CURL_VERSION_HTTP2 === CURL_VERSION_HTTP2)
```
To make feature availability checks more intuitive, this adds a new
`feature_list` key to `curl_version()` output array.
With it, checking for individual features availability is easier, and does
not require inspecting the availability of the `CURL_VERSION` constant and
the `features` key.
```php
!empty(curl_version()['feature_list']['HTTP2']);
```
