Rename hs->public_key.

This is an unhelpfully generic name. Rename it to match SSL_ECDH_CTX.
Unqualified "public key" is typically assumed to be the certificate.

Change-Id: I8ba8c3f2bb1343d1c006845a1110e833451c5a56
Reviewed-on: https://boringssl-review.googlesource.com/14564
Reviewed-by: Adam Langley <agl@google.com>

ssl/internal.h

diff --git a/ssl/internal.h b/ssl/internal.h
index 2504ca0..a6375a6 100644
--- a/ssl/internal.h
+++ b/ssl/internal.h
@@ -1014,10 +1014,10 @@
   uint8_t *key_share_bytes;
   size_t key_share_bytes_len;
 
-  /* public_key, for servers, is the key share to be sent to the client in TLS
-   * 1.3. */
-  uint8_t *public_key;
-  size_t public_key_len;
+  /* ecdh_public_key, for servers, is the key share to be sent to the client in
+   * TLS 1.3. */
+  uint8_t *ecdh_public_key;
+  size_t ecdh_public_key_len;
 
   /* peer_sigalgs are the signature algorithms that the peer supports. These are
    * taken from the contents of the signature algorithms extension for a server