Add test case I forgot for r115159 (support implicit includes along with PCH).

llvm-svn: 115247
diff --git a/clang/test/PCH/cmdline-include2.h b/clang/test/PCH/cmdline-include2.h
new file mode 100644
index 0000000..cf8e37b
--- /dev/null
+++ b/clang/test/PCH/cmdline-include2.h
@@ -0,0 +1 @@
+enum { x2 };