PDO refactoring for code simplification (#2522)

* PDO refactor

* Automatic prefix when using the syntax `_tableName`
* Uniformity: MySQL is now PDO::ATTR_EMULATE_PREPARES = false just like SQLite and PostgreSQL, with consequences such as only one statement per query
* Use PDO methods exec(), query(), prepare() + execute() in a more efficient way
* Remove auto-update SQL code for versions older than FreshRSS 1.5 (3 years old)
* The name of the default category is set in PHP instead of in the DB (simplies SQL and allows changing the name according to the FreshRSS language)
* Rename `->bd` to `->pdo` (less of a frenshism, and more informative)
* Fix some requests, which were not compatible with MySQL prepared statements

* Whitespace

* Fix syntax for PostgreSQL sequences

+ MySQL install

* Minor formatting

* Fix lastInsertId for PostgreSQL

* Use PHP 5.6+ const

Take advantage of https://github.com/FreshRSS/FreshRSS/pull/2527
https://www.php.net/manual/en/migration56.new-features.php

* A bit of forgotten PHP 5.6 simplification for cURL

* Forgotten $s

* Mini fix custom user config

https://github.com/FreshRSS/FreshRSS/pull/2490/files#r326290346

* More work on install.php but not finished

* install.php working

* More cleaning of PDO in install

* Even more simplification

Take advantage of PDO->exec() to run multiple statements

* Disallow changing the name of the default category

https://github.com/FreshRSS/FreshRSS/pull/2522#discussion_r326967724

1 files changed, 4 insertions, 6 deletions

diff --git a/p/f.php b/p/f.php
index b68109cd5..9947539c3 100644
--- a/p/f.php
+++ b/p/f.php
@@ -5,13 +5,11 @@ require(LIB_PATH . '/favicons.php');
 require(LIB_PATH . '/http-conditional.php');
 
 function show_default_favicon($cacheSeconds = 3600) {
-	global $default_favicon;
-
 	header('Content-Disposition: inline; filename="default_favicon.ico"');
 
-	$default_mtime = @filemtime($default_favicon);
+	$default_mtime = @filemtime(DEFAULT_FAVICON);
 	if (!httpConditional($default_mtime, $cacheSeconds, 2)) {
-		readfile($default_favicon);
+		readfile(DEFAULT_FAVICON);
 	}
 }
 
@@ -20,8 +18,8 @@ if (!ctype_xdigit($id)) {
 	$id = '0';
 }
 
-$txt = $favicons_dir . $id . '.txt';
-$ico = $favicons_dir . $id . '.ico';
+$txt = FAVICONS_DIR . $id . '.txt';
+$ico = FAVICONS_DIR . $id . '.ico';
 
 $ico_mtime = @filemtime($ico);
 $txt_mtime = @filemtime($txt);