OS: Rename B_USER_CLONEABLE_AREA to B_CLONEABLE_AREA.

It now lives in OS.h. The idea is that this will now be
accessible to userland applications, so userland memory
is protected from access by other processes, just as
kernel memory is.

No functional change (the constants are still the same,
though I've changed some to use shifts to make clear
which bits are allocated are which are unused.)

headers/private/system/vm_defs.h

@@ -29,13 +29,13 @@
 //	field is the only flag field, we currently use it for this.
 //	A cleaner approach would be appreciated - maybe just an official generic
 //	flags region in the protection field.
-#define B_OVERCOMMITTING_AREA	0x1000
-#define B_SHARED_AREA			0x2000
-/* 0x4000 was B_KERNEL_AREA until hrev52545 */
+#define B_OVERCOMMITTING_AREA	(1 << 12)
+#define B_SHARED_AREA			(1 << 13)
 
-#define B_USER_AREA_FLAGS		(B_USER_PROTECTION | B_OVERCOMMITTING_AREA)
+#define B_USER_AREA_FLAGS		\
+	(B_USER_PROTECTION | B_OVERCOMMITTING_AREA | B_CLONEABLE_AREA)
 #define B_KERNEL_AREA_FLAGS \
-	(B_KERNEL_PROTECTION | B_USER_CLONEABLE_AREA | B_SHARED_AREA)
+	(B_KERNEL_PROTECTION | B_SHARED_AREA)
 
 // mapping argument for several internal VM functions
 enum {