Fix mis-spelling of bits and types names in the vnode_pager_putpages().
The changes should not modify the generated code.

The pager->pgo_putpages() method takes int flags as its fourth
argument, while vnode_pager_putpages() used boolean_t (which is
typedef'ed to int).  The flags are from VM_PAGER_* namespace, while
vnode_pager_putpages() passed TRUE and OBJPC_SYNC to VOP_PUTPAGES(),
which both are numerically equal to VM_PAGER_PUT_SYNC.

Noted and reviewed by:	alc (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Update CAM CCB accounting for the new status quo.

devq_openings counter lost its meaning after allocation queues has gone.
held counter is still meaningful, but problematic to update due to separate
locking of CCB allocation and queuing.

To fix that replace devq_openings counter with allocated counter.  held is
now calculated on request as difference between number of allocated, queued
and active CCBs.

MFC after:	1 month
Added missing ZFS sysctls
* vfs.zfs.vdev.async_write_active_min_dirty_percent
* vfs.zfs.vdev.async_write_active_max_dirty_percent

Added validation of min / max for ZFS sysctl
* vfs.zfs.dirty_data_max_percent

MFC after:	3 days
sh: Add some const keywords.