ClangFormat: Simplify the dummy text for empty line heuristics

The text to fill the empty line mostly depends not on the
fact of being inside parenthesis or not but rather on the
last preceding meaningful character.

Let's check for this character and sometimes for the following
one to better understand the current context and pick the
proper dummy text.

With this behavior improvement we can better indent empty lines
inside initializer lists with empty lines inside.

Change-Id: Id2f27454ef56dfdf8c15b5efb14c4d09242908a9
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

tests/unit/unittest/clangformat-test.cpp

@@ -404,6 +404,19 @@ TEST_F(ClangFormat, IndentEmptyLineInsideParantheses)
                                              "    && b)"));
 }
 
+TEST_F(ClangFormat, EmptyLineInInitializerList)
+{
+    insertLines({"Bar foo{a,",
+                 "",
+                 "};"});
+
+    indenter.indentBlock(doc.findBlockByNumber(1), QChar::Null, TextEditor::TabSettings());
+
+    ASSERT_THAT(documentLines(), ElementsAre("Bar foo{a,",
+                                             "        ",
+                                             "};"));
+}
+
 TEST_F(ClangFormat, IndentFunctionBodyButNotFormatBeforeIt)
 {
     insertLines({"int foo(int a, int b,",