Retool the M_* flags to malloc() and the VM_ALLOC_* flags to

Retool the M_* flags to malloc() and the VM_ALLOC_* flags to
vm_page_alloc(), and vm_page_grab() and friends.

The M_* flags now have more flexibility, with the intent that we will start
using some of it to deal with NULL pointer return problems in the codebase
(CAM is especially bad at dealing with unexpected return values).  In
particular, add M_USE_INTERRUPT_RESERVE and M_FAILSAFE, and redefine
M_NOWAIT as a combination of M_ flags instead of its own flag.

The VM_ALLOC_* macros are now flags (0x01, 0x01, 0x04) rather then states
(1, 2, 3), which allows us to create combinations that the old interface
could not handle.