Build: Fix configure to handle LZMA1 dependency with LZMA2.

Now it gives an error if LZMA1 encoder/decoder is missing
when LZMA2 encoder/decoder was requested. Even better would
be LZMA2 implicitly enabling LZMA1 but it would need more code.
diff --git a/configure.ac b/configure.ac
index 53ae7be..5842882 100644
--- a/configure.ac
+++ b/configure.ac
@@ -141,11 +141,6 @@
 				;;
 		esac
 	done
-
-	# LZMA2 requires that LZMA1 is enabled.
-	test "x$enable_encoder_lzma2" = xyes && enable_encoder_lzma1=yes
-	test "x$enable_decoder_lzma2" = xyes && enable_decoder_lzma1=yes
-
 	AC_MSG_RESULT([$enable_decoders])
 fi