Tests: Add bad-1-lzma2-10.xz and also modify -9.xz.

tests/files/README

@@ -246,6 +246,13 @@
     properties in the third LZMA2 chunk.
 
     bad-1-lzma2-9.xz has LZMA2 stream that is truncated at the end of
-    a LZMA2 chunk and has no end marker. The uncompressed size of the
-    partial LZMA2 stream exceeds the value stored in the Block Header.
+    a LZMA2 chunk (no end marker). The uncompressed size of the partial
+    LZMA2 stream exceeds the value stored in the Block Header.
+
+    bad-1-lzma2-10.xz has LZMA2 stream that, from point of view of a
+    LZMA2 decoder, extends past the end of Block (and even the end of
+    the file). Uncompressed Size in Block Header is bigger than the
+    invalid LZMA2 stream may produce (even if a decoder reads until
+    the end of the file). The Check type is None to nullify certain
+    simple size-based sanity checks in a Block decoder.