[amiwm] add some initial comments of structure members.

Still have a long way to go.

client.h

@@ -6,6 +6,14 @@
 
 struct _Icon;
 struct _Scrn;
+
+/*
+ * struct _Client - application client information.
+ *
+ * @next: next client in list.
+ * @scr: virtual desktop this client belongs to.
+ * @colormap: current colormap.
+ */
 typedef struct _Client {
   struct _Client *next;
   struct _Scrn *scr;

screen.h

@@ -3,6 +3,18 @@
 
 #include "icon.h"
 
+/*
+ * Struct _Scrn - virtual desktop screen
+ *
+ * @root: root window for virtual desktop
+ * @back: background window
+ * @colormap: current colourmap
+ * @fh: font height for menu/window, including ascender/descender.
+ * @bh: title bar / menu bar height; fh + fixed padding.
+ * @icons: list of icons on this desktop.
+ * @firstselected: first selected icon on this desktop.
+ */
+
 typedef struct _Scrn {
   struct _Scrn *behind, *upfront;
   Window root, back, inputbox;