Add compact panels support

Add a configuration option that allows for switching to compact panel
mode. In this mode, all window labels are hidden, so that there's more
space for actual information.

This patch doesn't add a configuration menu entry and doesn't add any
documentation.

Implements FR#7.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/calcurse.h

@@ -147,7 +147,7 @@
 #define MAXDAYSPERMONTH 31
 
 /* Calendar window. */
-#define CALHEIGHT       12
+#define CALHEIGHT       8
 
 /* Key definitions. */
 #define CTRLVAL                 0x1F
@@ -250,6 +250,7 @@ struct conf {
   unsigned confirm_quit;
   unsigned confirm_delete;
   enum win default_panel;
+  unsigned compact_panels;
   unsigned system_dialogs;
   unsigned progress_bar;
   const char *editor;