Read multi-byte char group counts

Change-Id: Idc62382f1c814e9bd1466c9f7dda1fcc8ba4137d
diff --git a/native/src/binary_format.h b/native/src/binary_format.h
index 9944fa2..1d74998 100644
--- a/native/src/binary_format.h
+++ b/native/src/binary_format.h
@@ -61,7 +61,9 @@
 }
 
 inline int BinaryFormat::getGroupCountAndForwardPointer(const uint8_t* const dict, int* pos) {
-    return dict[(*pos)++];
+    const int msb = dict[(*pos)++];
+    if (msb < 0x80) return msb;
+    return ((msb & 0x7F) << 8) | dict[(*pos)++];
 }
 
 inline uint8_t BinaryFormat::getFlagsAndForwardPointer(const uint8_t* const dict, int* pos) {