Add AF_CONFIG_OPTION_USE_WARPER to control the autofit warper.

* devel/ftoption.h, include/freetype/config/ftoption.h
(AF_CONFIG_OPTION_USE_WARPER): New macro.
* src/autofit/aftypes.h (AF_USE_WARPER): Remove.

* src/autofit/*: s/AF_USE_WARPER/AF_CONFIG_OPTION_USE_WARPER/.

* src/autofit/afwarp.c [!AF_CONFIG_OPTION_USE_WARPER]: Replace dummy
variable assignment with a typedef.
diff --git a/src/autofit/autofit.c b/src/autofit/autofit.c
index 83b613e..bda2ab0 100644
--- a/src/autofit/autofit.c
+++ b/src/autofit/autofit.c
@@ -34,7 +34,7 @@
 #include "afloader.c"
 #include "afmodule.c"
 
-#ifdef AF_USE_WARPER
+#ifdef AF_CONFIG_OPTION_USE_WARPER
 #include "afwarp.c"
 #endif