patch 8.0.0148: wrong indent in C preprocessor with line continuation

Problem:    When a C preprocessor statement has two line continuations the
            following line does not have the right indent. (Ken Takata)
Solution:   Add the indent of the previous continuation line. (Hirohito
            Higashi)
diff --git a/src/testdir/test3.ok b/src/testdir/test3.ok
index 2f9572c..cfb519b 100644
--- a/src/testdir/test3.ok
+++ b/src/testdir/test3.ok
@@ -2080,3 +2080,17 @@
 	i;
 JSEND
 
+
+/* start of define */
+{
+}
+#define AAA \
+	BBB\
+	CCC
+
+#define CNT \
+	1 + \
+	2 + \
+	4
+/* end of define */
+