patch 7.4.1402

Problem:    GTK 3 is not supported.
Solution:   Add GTK 3 support. (Kazunobu Kuriyama)

src/gui.h

@@ -359,7 +359,9 @@ typedef struct Gui
 #endif
 
 #ifdef FEAT_GUI_GTK
+# ifndef USE_GTK3
     int		visibility;	    /* Is shell partially/fully obscured? */
+# endif
     GdkCursor	*blank_pointer;	    /* Blank pointer */
 
     /* X Resources */
@@ -381,7 +383,12 @@ typedef struct Gui
     GdkColor	*fgcolor;	    /* GDK-styled foreground color */
     GdkColor	*bgcolor;	    /* GDK-styled background color */
     GdkColor	*spcolor;	    /* GDK-styled special color */
+# ifdef USE_GTK3
+    cairo_surface_t *surface;       /* drawarea surface */
+    gboolean	     by_signal;     /* cause of draw operation */
+# else
     GdkGC	*text_gc;	    /* cached GC for normal text */
+# endif
     PangoContext     *text_context; /* the context used for all text */
     PangoFont	     *ascii_font;   /* cached font for ASCII strings */
     PangoGlyphString *ascii_glyphs; /* cached code point -> glyph map */