Fixed dlls/ntdll/cdrom.c compilation in Darwin by adding HAVE_IOKit
detection to configure and defining SENSEBUFLEN as kSenseDefaultSize
(which is corresponding IOKit enum value).

diff --git a/configure.ac b/configure.ac
index 175eadd..93d0fbd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -171,6 +171,7 @@
 dnl **** Check for header files ****
 
 AC_CHECK_HEADERS(\
+	IOKit/IOKitLib.h \
 	arpa/inet.h \
 	arpa/nameser.h \
 	asm/types.h \