Utf8: improved class doc comment wording

std/haxe/Utf8.hx

@@ -22,7 +22,7 @@
 package haxe;
 
 /**
-	Since all platforms does not guarantee that String always uses UTF-8 encoding, you
+	Since not all platforms guarantee that `String` always uses UTF-8 encoding, you
 	can use this crossplatform API to perform operations on such strings.
 **/
 class Utf8 {
@@ -44,7 +44,7 @@ class Utf8 {
 	}
 
 	/**
-		Returns the buffer converted to a String;
+		Returns the buffer converted to a String.
 	**/
 	public inline function toString() : String {
 		return __b;
@@ -109,4 +109,4 @@ class Utf8 {
 		return s.substr(pos,len);
 	}
 
-}
+}