Use newer autotools. Only build debug.c when --enable-debug.

.pc/ios/fficonfig.h.in

@@ -134,6 +134,9 @@
 /* Define to the one symbol short name of this package. */
 #undef PACKAGE_TARNAME
 
+/* Define to the home page for this package. */
+#undef PACKAGE_URL
+
 /* Define to the version of this package. */
 #undef PACKAGE_VERSION
 
@@ -176,6 +179,9 @@
 # endif
 #endif
 
+/* Define to `unsigned int' if <sys/types.h> does not define. */
+#undef size_t
+
 
 #ifdef HAVE_HIDDEN_VISIBILITY_ATTRIBUTE
 #ifdef LIBFFI_ASM