Reserve a bit in the FreeBSD feature control note for marking the

image as not compatible with ASLR.

Requested by:	emaste
Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Differential revision:	https://reviews.freebsd.org/D5603

sys/sys/elf_common.h

@@ -762,6 +762,9 @@ typedef struct {
 #define	NT_FREEBSD_ARCH_TAG	3
 #define	NT_FREEBSD_FEATURE_CTL	4
 
+/* NT_FREEBSD_FEATURE_CTL desc[0] bits */
+#define	NT_FREEBSD_FCTL_ASLR_DISABLE	0x00000001
+
 /* Values for n_type.  Used in core files. */
 #define	NT_PRSTATUS	1	/* Process status. */
 #define	NT_FPREGSET	2	/* Floating point registers. */