Fix various style issues following feedback

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2020)

ssl/statem/statem_clnt.c

diff --git a/ssl/statem/statem_clnt.c b/ssl/statem/statem_clnt.c
index 84dcf08..a3133ad 100644
--- a/ssl/statem/statem_clnt.c
+++ b/ssl/statem/statem_clnt.c
@@ -1360,7 +1360,7 @@
     const unsigned char *certstart, *certbytes;
     STACK_OF(X509) *sk = NULL;
     EVP_PKEY *pkey = NULL;
-    size_t chain;
+    size_t chainidx;
     unsigned int context = 0;
 
     if ((sk = sk_X509_new_null()) == NULL) {
@@ -1376,7 +1376,7 @@
         SSLerr(SSL_F_TLS_PROCESS_SERVER_CERTIFICATE, SSL_R_LENGTH_MISMATCH);
         goto f_err;
     }
-    for (chain = 0; PACKET_remaining(pkt); chain++) {
+    for (chainidx = 0; PACKET_remaining(pkt); chainidx++) {
         if (!PACKET_get_net_3(pkt, &cert_len)
             || !PACKET_get_bytes(pkt, &certbytes, cert_len)) {
             al = SSL_AD_DECODE_ERROR;
@@ -1411,7 +1411,7 @@
             if (!tls_collect_extensions(s, &extensions, EXT_TLS1_3_CERTIFICATE,
                                         &rawexts, &al)
                     || !tls_parse_all_extensions(s, EXT_TLS1_3_CERTIFICATE,
-                                                 rawexts, x, chain, &al))
+                                                 rawexts, x, chainidx, &al))
                 goto f_err;
         }
 

ssl/statem/statem_lib.c

diff --git a/ssl/statem/statem_lib.c b/ssl/statem/statem_lib.c
index cc5ca67..4b64541 100644
--- a/ssl/statem/statem_lib.c
+++ b/ssl/statem/statem_lib.c
@@ -354,7 +354,7 @@
     /*
      * If we have a certificate specific chain use it, else use parent ctx.
      */
-    if (cpk->chain)
+    if (cpk->chain != NULL)
         extra_certs = cpk->chain;
     else
         extra_certs = s->ctx->extra_certs;
@@ -366,7 +366,7 @@
     else
         chain_store = s->ctx->cert_store;
 
-    if (chain_store) {
+    if (chain_store != NULL) {
         X509_STORE_CTX *xs_ctx = X509_STORE_CTX_new();
 
         if (xs_ctx == NULL) {

ssl/statem/statem_srvr.c

diff --git a/ssl/statem/statem_srvr.c b/ssl/statem/statem_srvr.c
index 8b765a9..b3d6419 100644
--- a/ssl/statem/statem_srvr.c
+++ b/ssl/statem/statem_srvr.c
@@ -427,7 +427,7 @@
         return WRITE_TRAN_CONTINUE;
 
     case TLS_ST_SW_CERT:
-            st->hand_state = TLS_ST_SW_FINISHED;
+        st->hand_state = TLS_ST_SW_FINISHED;
         return WRITE_TRAN_CONTINUE;
 
     case TLS_ST_SW_FINISHED:
@@ -3139,7 +3139,7 @@
     const unsigned char *certstart, *certbytes;
     STACK_OF(X509) *sk = NULL;
     PACKET spkt, context;
-    size_t chain;
+    size_t chainidx;
 
     if ((sk = sk_X509_new_null()) == NULL) {
         SSLerr(SSL_F_TLS_PROCESS_CLIENT_CERTIFICATE, ERR_R_MALLOC_FAILURE);
@@ -3156,7 +3156,7 @@
         goto f_err;
     }
 
-    for (chain = 0; PACKET_remaining(&spkt) > 0; chain++) {
+    for (chainidx = 0; PACKET_remaining(&spkt) > 0; chainidx++) {
         if (!PACKET_get_net_3(&spkt, &l)
             || !PACKET_get_bytes(&spkt, &certbytes, l)) {
             al = SSL_AD_DECODE_ERROR;
@@ -3190,7 +3190,7 @@
             if (!tls_collect_extensions(s, &extensions, EXT_TLS1_3_CERTIFICATE,
                                         &rawexts, &al)
                     || !tls_parse_all_extensions(s, EXT_TLS1_3_CERTIFICATE,
-                                                 rawexts, x, chain, &al))
+                                                 rawexts, x, chainidx, &al))
                 goto f_err;
         }