Bug 622124 - implement flags for GSettings

Add a <flags> tag to the schema file format and a flags='' attribute to
go along with.  Add some extra test cases for those.

Add new g_settings_{get,set}_flags() calls and support binding to
GParamSpecFlags properties.  Add test cases.

gio/tests/testenum.h

@@ -5,3 +5,12 @@ typedef enum
   TEST_ENUM_BAZ,
   TEST_ENUM_QUUX
 } TestEnum;
+
+typedef enum
+{
+  TEST_FLAGS_NONE     = 0,
+  TEST_FLAGS_MOURNING = (1 << 0),
+  TEST_FLAGS_LAUGHING = (1 << 1),
+  TEST_FLAGS_TALKING  = (1 << 2),
+  TEST_FLAGS_WALKING  = (1 << 3)
+} TestFlags;