Add Text_Highlighter to Composer

- Fixes critical mistake in boot.php regarding set_include_path
- Fixes minor mistake in text.php regarding strpos order of arguments

Note: This change significantly increases Composer running time because
Text_Highlither is a PEAR package. I'm already planning to replace it
with scrivo/highlight.php.

composer.json

@@ -14,8 +14,15 @@
 	},
 	"require": {
 		"ezyang/htmlpurifier": "~4.7.0",
-		"mobiledetect/mobiledetectlib": "2.8.*"
+		"mobiledetect/mobiledetectlib": "2.8.*",
+		"pear-pear.php.net/Text_Highlighter": "*"
 	},
+	"repositories": [
+        {
+            "type": "pear",
+            "url": "https://pear.php.net"
+        }
+    ],
 	"autoload": {
 		"psr-4": {
 			"Friendica\\": "src/"