patch 8.2.3961: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/gui_haiku.cc b/src/gui_haiku.cc
index 6d973c5..1dd29b7 100644
--- a/src/gui_haiku.cc
+++ b/src/gui_haiku.cc
@@ -3847,7 +3847,7 @@
 
     if (name == 0 && be_fixed_font == 0) {
 	if (giveErrorIfMissing)
-			semsg(_(e_font), name);
+	    semsg(_(e_unknown_font_str), name);
 	return NOFONT;
     }
 
@@ -3914,7 +3914,7 @@
 
     if (count_font_styles(family) <= 0) {
 	if (giveErrorIfMissing)
-			semsg(_(e_font), font->name);
+	    semsg(_(e_unknown_font_str), font->name);
 	delete font;
 	return NOFONT;
     }