Fix up macros.

Macros need a healthy dose of parentheses to avoid expression-level
misparses. Most of this comes from the clang-tidy CL here:
https://android-review.googlesource.com/c/235696/

Also switch most of the macros to use do { ... } while (0) to avoid all
the excessive comma operators and statement-level misparses.

Change-Id: I4c2ee51e347d2aa8c74a2d82de63838b03bbb0f9
Reviewed-on: https://boringssl-review.googlesource.com/11660
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/x509_vfy.h b/include/openssl/x509_vfy.h
index 0a45aad..1182bc2 100644
--- a/include/openssl/x509_vfy.h
+++ b/include/openssl/x509_vfy.h
@@ -110,7 +110,7 @@
 */
 
 /* The following are legacy constants that should not be used. */
-#define X509_LU_RETRY		-1
+#define X509_LU_RETRY		(-1)
 #define X509_LU_FAIL		0
 
 #define X509_LU_X509		1