pmap/i386: Unbreak buildkernel

- Comment out pmap_change_attr function call.  Add notes about what
  needs fix.
- Minor style change.
route/inet: Dispatch PRCLONed route expiration to netisr
route/inet: Add comment about read/write shared global variables
kernel: Add a memattr argument to vm_page_alloc_contig()
drm: Move PROC_LOCK define to common file
drm: Locally implement VM_OBJECT_LOCK variants
drm: Import the ttm memory manager from FreeBSD

It is needed by some recent GPU drivers such as nouveau and radeon
for nvidia and AMD hardware
ttm porting: Fix include files
ttm porting: MPASS -> KKASSERT
ttm porting: malloc / free / printf

* printf() => kprintf()

* malloc() => kmalloc()

* free() => drm_free()
ttm porting: Translate locking primitives

* rw locks to lockmgr locks

* sx locks to lockmgr locks

* Some mtx locks to lockmgr locks

* Some mtx_locks to spinlocks

Some more locks could probably be converted to spinlocks but this
can be dangerous.
Better use lockmgr locks first and be sure the code runs without any
issue before trying to optimize it.
ttm porting: msleep => lksleep
ttm porting: Fix vm_page_alloc_contig() calls
ttm porting: Small changes (1/3)

* fix kern_psignal()

* fix sf_buf.h

* TAILQ_FOREACH_XXX_SAFE => TAILQ_FOREACH_XXX_MUTABLE()

* mb() => cpu_mfence()

* kernel_map => &kernel_map

* fix kmem_alloc_nofault() calls

* taskqueue_thread => taskqueue_thread[mycpuid]
ttm porting: Small changes (2/3)

* Remove vm_page_lock() and vm_page_unlock()

* vm_page_busy() => vm_page_busy_try()

* Replace kern_yield() by lwkt_yield()

* Remove vm_page_sleep() calls

* vm_pager_allocate() => swap_pager_alloc()

* vm_pager_get_pages() => vm_pager_get_page()

* Fix vm_pager_has_page() call
ttm porting: Small changes (3/3)

* Fix taskqueue_start_threads() calls

* Remove VPO_UNMANAGED

* Remove VM_ALLOC_WIRED and VM_ALLOC_NOOBJ

* Remove VM_ALLOC_NOBUSY

* Replace VPO_BUSY by PG_BUSY

* Fix calls to pmap_copy_page()

* Fix calls to pmap_zero_page()