<sys/types.h>: Make boolean_t kernel only type.
This effectively eliminates boolean_t from use in userland. Injecting
this type into userland codes often creates issues in DPorts where ports
are defining their own boolean_t type. Kernel headers now do not make
any references to this type even under _KERNEL_STRUCTURES.
If visibility is desired kernel headers can use __boolean_t that will
not conflict with 3rd-party software codes.
While there, make "struct pagerops" in vm/vm_pager.h kernel only, it is
only used below for pagertab that is already under _KERNEL.
UnifiedSplitRaw
