[autofit] Fix 'multi' compilation.

* src/autofit/ft-hb.c: Decorate with `FT_LOCAL_DEF`.
Add ANSI boilerplate code for otherwise empty file.
* src/autofit/ft-hb.h: Include `compiler-macros.h` and `freetype.h`.
Use `FT_BEGIN_HEADER` and `FT_END_HEADER`.
Decorate with `FT_LOCAL`.

* src/autofit/rules.mk (AUTOF_DRV_SRC): Add `ft-hb.c`.

src/autofit/ft-hb.c

@@ -92,7 +92,7 @@ hb_ft_face_create_ (FT_Face           ft_face,
   return face;
 }
 
-hb_font_t *
+FT_LOCAL_DEF(hb_font_t *)
 hb_ft_font_create_ (FT_Face           ft_face,
                     hb_destroy_func_t destroy)
 {
@@ -105,4 +105,11 @@ hb_ft_font_create_ (FT_Face           ft_face,
   return font;
 }
 
-#endif
+#else /* !FT_CONFIG_OPTION_USE_HARFBUZZ */
+
+/* ANSI C doesn't like empty source files */
+typedef int  _ft_hb_dummy;
+
+#endif /* !FT_CONFIG_OPTION_USE_HARFBUZZ */
+
+/* END */

src/autofit/ft-hb.h

@@ -29,7 +29,20 @@
 
 #include <hb.h>
 
-hb_font_t * hb_ft_font_create_ (FT_Face           ft_face,
-                                hb_destroy_func_t destroy);
+#include <freetype/internal/compiler-macros.h>
+#include <freetype/freetype.h>
 
-#endif
+
+FT_BEGIN_HEADER
+
+FT_LOCAL(hb_font_t *)
+hb_ft_font_create_ (FT_Face           ft_face,
+                    hb_destroy_func_t destroy);
+
+
+FT_END_HEADER
+
+#endif /* FT_HB_H */
+
+
+/* END */

src/autofit/rules.mk

@@ -39,6 +39,7 @@ AUTOF_DRV_SRC := $(AUTOF_DIR)/afblue.c   \
                  $(AUTOF_DIR)/afmodule.c \
                  $(AUTOF_DIR)/afranges.c \
                  $(AUTOF_DIR)/afshaper.c \
+                 $(AUTOF_DIR)/ft-hb.c
 
 # AUTOF driver headers
 #