[amiwm] add a new command action to rotate windows

This adds a command to iterate over the set of windows.  It's not
like alt-tab in ye olde windows world where you'd alt tab once to
switch between two windows, and then keep alt-tab'ing with alt down
to go through the window list.  For now it just literally iterates
through those windows.

This makes it a lot easier to work with a large number of open
windows without having to constantly use the mouse.

kbdlexer.l

@@ -41,6 +41,8 @@ int parse_keyword(char *str, YYSTYPE *val)
      { "back", (mdfuncp)md_back },
      { "front", (mdfuncp)md_front },
      { "iconify", (mdfuncp)md_iconify },
+     { "lowerwindow", (mdfuncp)md_rotate_window_lower },
+     { "raisewindow", (mdfuncp)md_rotate_window_raise },
      { "rotatescreens", (mdfuncp)k_rotscreens },
    };
 #define N_FUNC (sizeof(functab)/sizeof(functab[0]))