fix broken font matching due to a use-after-free

f3184ba introduced a use-after-
free bug. Pango does not copy the string when you use the _static
version of pango_font_description_set_family. Font selection was
not working for me at all.

src/register_font.cc

@@ -303,7 +303,7 @@ get_pango_font_description(unsigned char* filepath) {
  return NULL;
  }
 
- pango_font_description_set_family_static(desc, family);
+ pango_font_description_set_family(desc, family);
  free(family);
  pango_font_description_set_weight(desc, get_pango_weight(table->usWeightClass));
  pango_font_description_set_stretch(desc, get_pango_stretch(table->usWidthClass));