[PATCH] string: Improve memchr random test

[Wilco Dijkstra]

Add matches before the start to ensure the memchr test checks they do not
result in false matches or missed matches.

---

diff --git a/string/test-memchr.c b/string/test-memchr.c
index df9ce0f22c04c73472b134e89585c7557cd00dfc..42d18a596f850a5871dcbb2903153b59a8153d72 100644
--- a/string/test-memchr.c
+++ b/string/test-memchr.c
@@ -177,6 +177,11 @@ do_random_tests (void)
 	    }
 	}
 
+      /* Add matching chars before the start to improve test coverage.  */
+      i = random () & 31;
+      if (i < align)
+	p[i] = seek_char;
+
       if (pos < len)
 	{
 	  size_t r = random ();