If we have new features introduced by C11, use them

Instead of using hacks or compiler-specific features, if we have
standard features as defined in ISO C11, use them.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/asm/parser.c b/asm/parser.c
index 7b4cc5c..bc8ba50 100644
--- a/asm/parser.c
+++ b/asm/parser.c
@@ -492,7 +492,7 @@
     if (i == TOKEN_EOS)
         goto fail;
 
-    nasm_build_assert(P_none != 0);
+    nasm_build_assert(P_none == 0);
     memset(result->prefixes, P_none, sizeof(result->prefixes));
     result->times = 1L;