Update NSS to 3.38

- Added HACL*Poly1305 32-bit (INRIA/Microsoft)
- Updated to final TLS 1.3 draft version (28)
- Removed TLS 1.3 prerelease draft limit check
- Removed NPN code
- Enabled dev/urandom-only RNG on Linux with NSS_SEED_ONLY_DEV_URANDOM for non-standard environments
- Fixed several bugs with TLS 1.3 negotiation
- Updated internal certificate store
- Added support for the TLS Record Size Limit Extension.
- Fixed CVE-2018-0495
- Various security fixes in the ASN.1 code.

security/nss/lib/ssl/sslt.h

@@ -432,6 +432,7 @@ typedef enum {
     ssl_signed_cert_timestamp_xtn = 18,
     ssl_padding_xtn = 21,
     ssl_extended_master_secret_xtn = 23,
+    ssl_record_size_limit_xtn = 28,
     ssl_session_ticket_xtn = 35,
     /* 40 was used in draft versions of TLS 1.3; it is now reserved. */
     ssl_tls13_pre_shared_key_xtn = 41,
@@ -454,7 +455,7 @@ typedef enum {
 /* SSL_MAX_EXTENSIONS includes the maximum number of extensions that are
  * supported for any single message type.  That is, a ClientHello; ServerHello
  * and TLS 1.3 NewSessionTicket and HelloRetryRequest extensions have fewer. */
-#define SSL_MAX_EXTENSIONS 20
+#define SSL_MAX_EXTENSIONS 21
 
 /* Deprecated */
 typedef enum {