Escape U+200E and U+200F (#506)

Fixes #502

Author: bgotink

tests/benchmarks/html-standard-compact.kdl

@@ -491685,7 +491685,7 @@ html lang=en-US-x-hixie {
 						}
 						td " U+0200E "
 						td {
-							span class=glyph "‎"
+							span class=glyph "\u{200e}"
 						}
 					}
 					tr id=entity-lrtri {
@@ -497373,7 +497373,7 @@ html lang=en-US-x-hixie {
 						}
 						td " U+0200F "
 						td {
-							span class=glyph "‏"
+							span class=glyph "\u{200f}"
 						}
 					}
 					tr id=entity-rmoust {