Accept "default" as font family value in XRC.

Map it to wxFONTFAMILY_DEFAULT, just as we do for all other wxFontFamily enum
elements.

Closes #16549.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77686 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/overviews/xrc_format.h

@@ -401,8 +401,8 @@ and can be one of the following "sub-properties":
 @row3col{weight, enum,
     One of "normal", "bold" or "light" (default: normal).}
 @row3col{family, enum,
-    One of "roman", "script", "decorative", "swiss", "modern" or "teletype"
-    (default: roman).}
+    One of "default", "roman", "script", "decorative", "swiss", "modern" or "teletype"
+    (default: default).}
 @row3col{underlined, @ref overview_xrcformat_type_bool,
     Whether the font should be underlined (default: 0).}
 @row3col{face, ,