* Introduced new area creation flag CREATE_AREA_DONT_COMMIT_MEMORY.

map_backing_store() doesn't commit memory when this flag is given.
* Used the new flag vm_copy_area(): We no longer commit memory for read-only
  areas. This prevents read-only mapped files from suddenly requiring memory
  after fork(). Might improve the situation on machines with very little RAM
  a bit.
  We should probably mark writable copies over-committing, since the usual
  case is fork() + exec() where the child normally doesn't need more than a
  few pages until calling exec(). That would significantly reduce the memory
  requirement for jamming the Haiku tree.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@36651 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/vm/vm.h

@@ -32,6 +32,7 @@ struct VMPageWiringInfo;
 #define CREATE_AREA_UNMAP_ADDRESS_RANGE	0x02
 #define CREATE_AREA_DONT_CLEAR			0x04
 #define CREATE_AREA_PRIORITY_VIP		0x08
+#define CREATE_AREA_DONT_COMMIT_MEMORY	0x10
 
 // memory/page allocation priorities
 #define VM_PRIORITY_USER	0