Fix wm_size-hints race between KDE/KWin and Gtk+ 3.

Fix wm_size-hints race between KDE/KWin and Gtk+ 3.

* emacsgtkfixed.c: State that this is only used with Gtk+3.
(_EmacsFixedPrivate): Remove minwidth/height.
Add struct frame *f.
(emacs_fixed_init): Initialize priv->f.
(get_parent_class, emacs_fixed_set_min_size): Remove.
(emacs_fixed_new): Set priv->f to argument.
(emacs_fixed_get_preferred_width)
(emacs_fixed_get_preferred_height): Use min_width/height from
frames size_hint to set minimum and natural.
(XSetWMSizeHints, XSetWMNormalHints): Override these functions
and use min_width/height from frames size_hint to set
min_width/height (Bug#8919).

* emacsgtkfixed.h: State that this is only used with Gtk+3.
(emacs_fixed_set_min_size): Remove.
(emacs_fixed_new): Take frame as argument.

* gtkutil.c (xg_create_frame_widgets): Pass f to emacs_fixed_new.
(x_wm_set_size_hint): Remove call to emacs_fixed_set_min_size. Fix
indentation.