Fix PR5982, a refacto in checking for '=' in a -D argument.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@93088 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Frontend/macros.c b/test/Frontend/macros.c
new file mode 100644
index 0000000..3170797
--- /dev/null
+++ b/test/Frontend/macros.c
@@ -0,0 +1,4 @@
+// RUN: %clang_cc1 -DA= -DB=1 -verify -fsyntax-only %s
+
+int a[(B A) == 1 ? 1 : -1];
+