* testsuite/grep/grep-handles-binary-files: Read input from a pipe.

* testsuite/grep/grep-matches-NUL: Likewise.

testsuite/grep/grep-handles-binary-files

@@ -1,2 +1 @@
-echo -e '\0foo' >foo
-busybox grep foo foo
+echo -e '\0foo' | busybox grep foo

testsuite/grep/grep-matches-NUL

@@ -1,3 +1,2 @@
 # XFAIL
-echo -e '\0' >foo
-busybox grep . foo
+echo -e '\0' | busybox grep .