Fix references to NSA Suite B Implementer's Guides.

The reference in the ECDSA code was copy/pasted from the ECDH code,
which was referencing (of course) the ECDH guide. Fix it to refer to
the ECDSA guide.

Also, the NSA reorganized their website and now their ECDH guide is
gone and the ECDSA guide is not available at a stable, fixed, URL,
so remove the links.

src/ec/suite_b/ecdh.rs

@@ -37,12 +37,10 @@ macro_rules! ecdh {
         /// Public keys are validated during key agreement as described in
         /// [NIST Special Publication 800-56A, revision
         /// 2](http://csrc.nist.gov/groups/ST/toolkit/documents/SP800-56Arev1_3-8-07.pdf)
-        /// Section 5.6.2.5 and the NSA's [Suite B Implementer's Guide to NIST
-        /// SP
-        /// 800-56A](https://www.nsa.gov/ia/_files/suiteb_implementer_g-113808.pdf)
-        /// Appendix B.3. Note that, as explained in the NSA guide, "partial"
-        /// validation is equivalent to "full" validation for prime-order
-        /// curves like this one.
+        /// Section 5.6.2.5 and the NSA's "Suite B Implementer's Guide to NIST
+        /// SP 800-56A," Appendix B.3. Note that, as explained in the NSA
+        /// guide, "partial" validation is equivalent to "full" validation for
+        /// prime-order curves like this one.
         ///
         /// TODO: Each of the encoded coordinates are verified to be the
         /// correct length, but values of the allowed length that haven't been

src/ec/suite_b/ecdsa.rs

@@ -69,11 +69,10 @@ macro_rules! ecdsa {
         /// Public keys are validated during key agreement as described in
         /// [NIST Special Publication 800-56A, revision
         /// 2](http://csrc.nist.gov/groups/ST/toolkit/documents/SP800-56Arev1_3-8-07.pdf)
-        /// Section 5.6.2.5 and the [Suite B Implementer's Guide to NIST SP
-        /// 800-56A](https://www.nsa.gov/ia/_files/suiteb_implementer_g-113808.pdf)
-        /// Appendix B.3. Note that, as explained in the NSA guide, "partial"
-        /// validation is equivalent to "full" validation for prime-order
-        /// curves like this one.
+        /// Section 5.6.2.5 and the NSA's "Suite B implementer's guide to FIPS
+        /// 186-3," Appendix A.3. Note that, as explained in the NSA guide,
+        /// "partial" validation is equivalent to "full" validation for
+        /// prime-order curves like this one.
         ///
         /// The signature will be parsed as a DER-encoded `Ecdsa-Sig-Value` as
         /// described in [RFC 3279 Section