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

Reviewed-by: Tim Hudson <tjh@openssl.org>
diff --git a/crypto/x509v3/v3_bitst.c b/crypto/x509v3/v3_bitst.c
index eb6d0f3..9072b42 100644
--- a/crypto/x509v3/v3_bitst.c
+++ b/crypto/x509v3/v3_bitst.c
@@ -112,7 +112,7 @@
     ASN1_BIT_STRING *bs;
     int i;
     BIT_STRING_BITNAME *bnam;
-    if (!(bs = ASN1_BIT_STRING_new())) {
+    if ((bs = ASN1_BIT_STRING_new()) == NULL) {
         X509V3err(X509V3_F_V2I_ASN1_BIT_STRING, ERR_R_MALLOC_FAILURE);
         return NULL;
     }