Use p==NULL not !p (in if statements, mainly)

Reviewed-by: Tim Hudson <tjh@openssl.org>
diff --git a/apps/s_client.c b/apps/s_client.c
index a24d2f3..b257727 100644
--- a/apps/s_client.c
+++ b/apps/s_client.c
@@ -345,7 +345,8 @@
 {
     SRP_ARG *srp_arg = (SRP_ARG *)arg;
     BIGNUM *N = NULL, *g = NULL;
-    if (!(N = SSL_get_srp_N(s)) || !(g = SSL_get_srp_g(s)))
+
+    if (((N = SSL_get_srp_N(s)) == NULL) || ((g = SSL_get_srp_g(s)) == NULL))
         return 0;
     if (srp_arg->debug || srp_arg->msg || srp_arg->amp == 1) {
         BIO_printf(bio_err, "SRP parameters:\n");