patch 8.1.0743: giving error messages is not flexible

Problem:    Giving error messages is not flexible.
Solution:   Add semsg().  Change argument from "char_u *" to "char *", also
            for msg() and get rid of most MSG macros. (Ozaki Kiichi, closes
            #3302)  Also make emsg() accept a "char *" argument.  Get rid of
            an enormous number of type casts.

src/gui_photon.c

@@ -2937,7 +2937,7 @@ gui_mch_get_font(char_u *vim_font_name, int report_error)
     }
 
     if (report_error)
-	EMSG2(e_font, vim_font_name);
+	semsg(e_font, vim_font_name);
 
     return FAIL;
 }