patch 7.4.2243
Problem:    Warning for assigning negative value to unsigned. (Danek Duvall)
Solution:   Make cterm_normal_fg_gui_color and _bg_ guicolor_T, cast to long_u
            only when an unsigned is needed.
diff --git a/src/proto/gui_photon.pro b/src/proto/gui_photon.pro
index b03479c..7681b87 100644
--- a/src/proto/gui_photon.pro
+++ b/src/proto/gui_photon.pro
@@ -25,7 +25,7 @@
 void gui_mch_mousehide(int hide);
 void gui_mch_getmouse(int *x, int *y);
 void gui_mch_setmouse(int x, int y);
-long_u gui_mch_get_rgb(guicolor_T pixel);
+guicolor_T gui_mch_get_rgb(guicolor_T pixel);
 void gui_mch_new_colors(void);
 guicolor_T gui_mch_get_color(char_u *name);
 void gui_mch_set_fg_color(guicolor_T color);