Fix misc styleguide issues and add missing header files

Signed-off-by: Sohaib Mohamed <sohaib.amhmd@gmail.com>

ScreenManager.c

@@ -16,6 +16,7 @@ in the source distribution for its full text.
 
 #include "CRT.h"
 #include "FunctionBar.h"
+#include "Macros.h"
 #include "Object.h"
 #include "Platform.h"
 #include "ProcessList.h"

ScreensPanel.c

@@ -6,16 +6,17 @@ in the source distribution for its full text.
 */
 
 #include "ScreensPanel.h"
-#include "Platform.h"
 
-#include "CRT.h"
-#include "XUtils.h"
-
-#include <assert.h>
 #include <stdlib.h>
 #include <ctype.h>
 #include <string.h>
 
+#include "CRT.h"
+#include "FunctionBar.h"
+#include "Hashtable.h"
+#include "ProvideCurses.h"
+#include "XUtils.h"
+
 
 ObjectClass ScreenListItem_class = {
    .extends = Class(ListItem),

ScreensPanel.h

@@ -7,11 +7,14 @@ Released under the GNU GPL, see the COPYING file
 in the source distribution for its full text.
 */
 
+#include <stdbool.h>
+
+#include "ColumnsPanel.h"
+#include "ListItem.h"
+#include "Object.h"
 #include "Panel.h"
 #include "ScreenManager.h"
-#include "ColumnsPanel.h"
 #include "Settings.h"
-#include "ListItem.h"
 
 #ifndef SCREEN_NAME_LEN
 #define SCREEN_NAME_LEN 20