Fix handling of {unwrap} tags in word_wrap() functions

* in Email library: these tags were not removed
* in text helper: simplified code
diff --git a/system/helpers/text_helper.php b/system/helpers/text_helper.php
index 7e15c19..1d0605d 100644
--- a/system/helpers/text_helper.php
+++ b/system/helpers/text_helper.php
@@ -430,12 +430,12 @@
 		// If the current word is surrounded by {unwrap} tags we'll
 		// strip the entire chunk and replace it with a marker.
 		$unwrap = array();
-		if (preg_match_all('|(\{unwrap\}.+?\{/unwrap\})|s', $str, $matches))
+		if (preg_match_all('|\{unwrap\}(.+?)\{/unwrap\}|s', $str, $matches))
 		{
 			for ($i = 0, $c = count($matches[0]); $i < $c; $i++)
 			{
 				$unwrap[] = $matches[1][$i];
-				$str = str_replace($matches[1][$i], '{{unwrapped'.$i.'}}', $str);
+				$str = str_replace($matches[0][$i], '{{unwrapped'.$i.'}}', $str);
 			}
 		}
 
@@ -491,8 +491,7 @@
 			}
 		}
 
-		// Remove the unwrap tags and return
-		return str_replace(array('{unwrap}', '{/unwrap}'), '', $output);
+		return $output;
 	}
 }