replace retired gdk_gl_font_use_pango_font with pango_font_map_load_font
https://github.com/Garux/netradiant-custom/commit/a0a47640b0270d9377273f4fcb714a787300b7ac

Index: src/tools/radiant/libs/gtkutil/glfont.cpp
--- src/tools/radiant/libs/gtkutil/glfont.cpp.orig
+++ src/tools/radiant/libs/gtkutil/glfont.cpp
@@ -23,6 +23,7 @@
 #include <GL/gl.h>
 #include "debugging/debugging.h"
 #include <gtk/gtkglwidget.h>
+#include <pango-1.0/pango/pangoft2.h>
 
 GLFont glfont_create (const std::string& font_string)
 {
@@ -31,7 +32,10 @@ GLFont glfont_create (const std::string& font_string)
 
 	PangoFontDescription* font_desc = pango_font_description_from_string(font_string.c_str());
 
-	PangoFont* font = gdk_gl_font_use_pango_font(font_desc, 0, 256, font_list_base);
+	PangoFontMap *fontmap = pango_ft2_font_map_new();
+	pango_ft2_font_map_set_resolution(PANGO_FT2_FONT_MAP(fontmap), 72, 72);
+	PangoContext *ft2_context = pango_font_map_create_context(fontmap);
+	PangoFont* font = pango_font_map_load_font(fontmap, ft2_context, font_desc);
 
 	if (font != 0) {
 		PangoFontMetrics* font_metrics = pango_font_get_metrics(font, 0);
