Fix off-by-one in LZ decoder.

Fortunately, this bug had no security risk other than accepting
some corrupt files as valid.

src/liblzma/lz/lz_decoder.h

@@ -126,7 +126,7 @@
 static inline bool
 dict_is_distance_valid(const lzma_dict *const dict, const size_t distance)
 {
-	return dict->full >= distance;
+	return dict->full > distance;
 }