Implement cairo_font_face_get_type.

Add font type to font_face_backend.
Also export new CAIRO_FONT_TYPE_TOY.

src/cairo-atsui-font.c

@@ -94,6 +94,7 @@ _cairo_atsui_font_face_scaled_font_create (void	*abstract_face,
 }
 
 static const cairo_font_face_backend_t _cairo_atsui_font_face_backend = {
+    CAIRO_FONT_TYPE_ATSUI,
     _cairo_atsui_font_face_destroy,
     _cairo_atsui_font_face_scaled_font_create
 };

src/cairo-font.c

@@ -130,6 +130,12 @@ cairo_font_face_destroy (cairo_font_face_t *font_face)
     free (font_face);
 }
 
+cairo_font_type_t
+cairo_font_face_get_type (cairo_font_face_t *font_face)
+{
+    return font_face->backend->type;
+}
+
 /**
  * cairo_font_face_status:
  * @font_face: a #cairo_font_face_t
@@ -409,6 +415,7 @@ _cairo_toy_font_face_scaled_font_create (void                *abstract_font_face
 }
 
 static const cairo_font_face_backend_t _cairo_toy_font_face_backend = {
+    CAIRO_FONT_TYPE_TOY,
     _cairo_toy_font_face_destroy,
     _cairo_toy_font_face_scaled_font_create
 };

src/cairo-ft-font.c

@@ -2004,6 +2004,7 @@ _cairo_ft_font_face_scaled_font_create (void                     *abstract_face,
 }
 
 static const cairo_font_face_backend_t _cairo_ft_font_face_backend = {
+    CAIRO_FONT_TYPE_FT,
     _cairo_ft_font_face_destroy,
     _cairo_ft_font_face_scaled_font_create
 };

src/cairo-win32-font.c

@@ -1398,6 +1398,7 @@ _cairo_win32_font_face_scaled_font_create (void			*abstract_face,
 }
 
 static const cairo_font_face_backend_t _cairo_win32_font_face_backend = {
+    CAIRO_FONT_TYPE_WIN32,
     _cairo_win32_font_face_destroy,
     _cairo_win32_font_face_scaled_font_create
 };

src/cairo.h

@@ -928,6 +928,7 @@ cairo_font_face_status (cairo_font_face_t *font_face);
  * of the wrong type is undefined.
  */
 typedef enum _cairo_font_type {
+    CAIRO_FONT_TYPE_TOY,
     CAIRO_FONT_TYPE_FT,
     CAIRO_FONT_TYPE_WIN32,
     CAIRO_FONT_TYPE_ATSUI

src/cairoint.h

@@ -464,6 +464,7 @@ struct _cairo_scaled_font {
 };
 
 struct _cairo_font_face {
+    /* hash_entry must be first */
     cairo_hash_entry_t hash_entry;
     cairo_status_t status;
     int ref_count;
@@ -555,6 +556,8 @@ struct _cairo_scaled_font_backend {
 };
 
 struct _cairo_font_face_backend {
+    cairo_font_type_t	type;
+
     /* The destroy() function is allowed to resurrect the font face
      * by re-referencing. This is needed for the FreeType backend.
      */