AU: Switch signature verification from external openssl to library.

This avoids writing data to temp files, invoking an external process and reading
data from temporary files. This is cleaner, and improves marginally performance
and security.

BUG=9928
TEST=unit tests, emerge-arm-generic

Change-Id: I7b7d6632e23a1cbcc9a281f883279555583dd344

Review URL: http://codereview.chromium.org/5633001
diff --git a/payload_signer_unittest.cc b/payload_signer_unittest.cc
index 8121cae..f803156 100644
--- a/payload_signer_unittest.cc
+++ b/payload_signer_unittest.cc
@@ -88,7 +88,7 @@
   }
 }
 
-TEST(PayloadSignerTest, RunAsRootVerifySignatureTest) {
+TEST(PayloadSignerTest, VerifySignatureTest) {
   vector<char> signature_blob;
   SignSampleData(&signature_blob);