[ticket/15424] Multiple typo fixes in docs & comments

Fixed typos in some docs, guidelines, some non-user-facing files.

PHPBB3-15424

phpBB/phpbb/template/context.php

@@ -87,7 +87,7 @@ class context
 	}
 
 	/**
-	* Retreive a single scalar value from a single key.
+	* Retrieve a single scalar value from a single key.
 	*
 	* @param string $varname Variable name
 	* @return mixed Variable value, or null if not set
@@ -149,7 +149,7 @@ class context
 			{
 				// If the key name is lowercase and the data is an array,
 				// it could be a template loop. So we set the S_NUM_ROWS there
-				// aswell.
+				// as well.
 				if ($sub_block_name === strtolower($sub_block_name) && is_array($sub_block))
 				{
 					$this->set_num_rows($sub_block);