Revamp the window-resize behaviour UI so there are only three states

rather than four. Should fix all sorts of bugs, since the fourth
(and default!) state was behaving weirdly and nobody liked it.

[originally from svn r1307]

putty.h

@@ -303,8 +303,7 @@ typedef struct {
     int bellovl_s;		       /* period of silence to re-enable bell (s) */
     char bell_wavefile[FILENAME_MAX];
     int scrollbar;
-    int locksize;
-    int lockfont;
+    enum { RESIZE_TERM, RESIZE_DISABLED, RESIZE_FONT } resize_action;
     int bce;
     int blinktext;
     int win_name_always;