Fix off-by-one in hex-parsing.

src/scanner-base.h

Index: src/scanner-base.h
diff --git a/src/scanner-base.h b/src/scanner-base.h
index 4952f1cd650cea9f9447c01a75c95ad7e2f9aa5c..61b1fddda9331837f122028eda31972b80b6177c 100644
--- a/src/scanner-base.h
+++ b/src/scanner-base.h
@@ -48,7 +48,7 @@ inline int HexValue(uc32 c) {
   c -= '0';
   if (static_cast<unsigned>(c) <= 9) return c;
   c = (c | 0x20) - ('a' - '0');  // detect 0x11..0x16 and 0x31..0x36.
-  if (static_cast<unsigned>(c) <= 6) return c + 10;
+  if (static_cast<unsigned>(c) <= 5) return c + 10;
   return -1;
 }