MFC r289568, r300676, r300677, r300719, r300720 and r300721:
Implement LinuxKPI module parameters as SYSCTLs.

The bool module parameter is no longer supported, because there is no
equivalent in FreeBSD 10-stable. These are converted into "int" type.

There are two macros available which control the behaviour of the
LinuxKPI module parameters:

- LINUXKPI_PARAM_PARENT allows the consumer to set the SYSCTL parent
where the modules parameters will be created.

- LINUXKPI_PARAM_PREFIX defines a parameter name prefix, which is
added to all created module parameters.

The LinuxKPI module parameters also have a permissions value.
If any write bits are set we are allowed to modify the module
parameter runtime. Reflect this when creating the static SYSCTL
nodes.

The module_param_call() function is no longer supported.

Sponsored by: Mellanox Technologies

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Enable ib_dev.mmap function

Removed the ifdef linux from this function.
Added stub function for contiguous pages to avoid compilation
errors.

Submitted by: Orit Moskovich (oritm mellanox.com)
Approved by: re

Switch the vm_object mutex to be a rwlock. This will enable in the
future further optimizations where the vm_object lock will be held
in read mode most of the time the page cache resident pool of pages
are accessed for reading purposes.

The change is mostly mechanical but few notes are reported:
* The KPI changes as follow:
- VM_OBJECT_LOCK() -> VM_OBJECT_WLOCK()
- VM_OBJECT_TRYLOCK() -> VM_OBJECT_TRYWLOCK()
- VM_OBJECT_UNLOCK() -> VM_OBJECT_WUNLOCK()
- VM_OBJECT_LOCK_ASSERT(MA_OWNED) -> VM_OBJECT_ASSERT_WLOCKED()
(in order to avoid visibility of implementation details)
- The read-mode operations are added:
VM_OBJECT_RLOCK(), VM_OBJECT_TRYRLOCK(), VM_OBJECT_RUNLOCK(),
VM_OBJECT_ASSERT_RLOCKED(), VM_OBJECT_ASSERT_LOCKED()
* The vm/vm_pager.h namespace pollution avoidance (forcing requiring
sys/mutex.h in consumers directly to cater its inlining functions
using VM_OBJECT_LOCK()) imposes that all the vm/vm_pager.h
consumers now must include also sys/rwlock.h.
* zfs requires a quite convoluted fix to include FreeBSD rwlocks into
the compat layer because the name clash between FreeBSD and solaris
versions must be avoided.
At this purpose zfs redefines the vm_object locking functions
directly, isolating the FreeBSD components in specific compat stubs.

The KPI results heavilly broken by this commit. Thirdy part ports must
be updated accordingly (I can think off-hand of VirtualBox, for example).

Sponsored by: EMC / Isilon storage division
Reviewed by: jeff
Reviewed by: pjd (ZFS specific review)
Discussed with: alc
Tested by: pho

- Merge in OFED 1.5.3 from projects/ofed/head