[parser] implement error reporting for Scanner errors

src/messages.h

Index: src/messages.h
diff --git a/src/messages.h b/src/messages.h
index 23aab886ce34f96690b548e6fea8df424981334e..dac623fa8f3199c5fad858775e5b5bced0fcd50a 100644
--- a/src/messages.h
+++ b/src/messages.h
@@ -464,6 +464,9 @@ class CallSite {
   T(UnterminatedTemplate, "Unterminated template literal")                     \
   T(UnterminatedTemplateExpr, "Missing } in template expression")              \
   T(FoundNonCallableHasInstance, "Found non-callable @@hasInstance")           \
+  T(InvalidHexEscapeSequence, "Invalid hexadecimal escape sequence")           \
+  T(InvalidUnicodeEscapeSequence, "Invalid Unicode escape sequence")           \
+  T(UndefinedUnicodeCodePoint, "Undefined Unicode code-point")                 \
   /* EvalError */                                                              \
   T(CodeGenFromStrings, "%")                                                   \
   /* URIError */                                                               \