Fix #211

Patched by importing latest msun version

test/test-211.c

@@ -0,0 +1,12 @@
+#include <stdio.h>
+#include <math.h>
+#include <assert.h>
+
+int
+main()
+{
+  float x = 0xd.65874p-4f;
+  float y = 4.0f;
+  float z = powf (x, y);
+  assert(z==0x1.f74424p-2);
+}