Corrected doc
Add is_curl_available

function is_curl_available
Returns true if all curl functions used in the project are defined, false otherwise.

I don't know if it's better to check all functions or only one (curl_init for example).
Modify tests in install.php

Move pdo_sqlite test in functions.php.
Add curl test in install.php.
Correct syntax error
Correct tab
Modify curl checker.

is_curl_available is now know as check_curl_availability.
check_curl_availability returns null if there's no error, or an array of disabled and needed curl functions otherwise.

install.php now lists disabled needed curl functions in error message.
Add missing not in check_curl_availability
Sort feeds in menu by alphabetical order
Add title argument for feeds description
Move the feeds sort from index.php to inc/feeds.php in get_feeds()
Merge pull request #77 from Niols/master

Make the tests during installation more complete