MFC r259953:
Fix accounting for the negative cache entries when reusing v_cache_dd.
MFC r259792:
  Remove references to SUP_UPDATE and CVS_UPDATE.
  Include base svn when evaluating if svn(1) exists.

Sponsored by:	The FreeBSD Foundation
MFC r259464:
Fix periodic per-CPU timers startup on boot.
Revert r258396 : teach iconv about a WCHAR_T pseudo-type
MFC r260015:

In libc++'s type_traits header, avoid warnings (activated by our use of
-Wsystem-headers) about potential keyword compatibility problems, by
adding a __libcpp prefix to the applicable identifiers.

Upstream is still debating about this, but we need it now, to be able to
import clang 3.4.
MFC r260003:

In libiconv_modules, surround unused static _citrus_XXX_pack_state() and
_citrus_XXX_unpack_state() functions with #if 0, for now.
MFC r260016:

Remove superfluous old-style rcsid[] from if_sk.c.  There is already an
__FBSDID() at the top of the file.
MFC r260017:

Mark unused static inline functions defined by the PCTRIE_DEFINE() macro
as __unused, so warnings about them are avoided.
MFC r260020:

For sys/dev/drm2/radeon, only use -fms-extensions with gcc.  This flag
is only to stop gcc complaining about anonymous unions, which clang does
not do.  For clang 3.4 however, -fms-extensions enables the Microsoft
__wchar_t type, which clashes with our own types.h.

MFC r260102:

Similar to r260020, only use -fms-extensions with gcc, for all other
modules which require this flag to compile.  Use a GCC_MS_EXTENSIONS
variable, defined in kern.pre.mk, which can be used to easily supply the
flag (or not), depending on the compiler type.
MFC r260019:

For some files under sys/dev/drm2/i915, turn off warnings about unused
functions and variables, since they are contributed code.
MFC r260025:

Disable warning about unused functions for ar9300_reset.c for now.
MFC r260026:

Disable warning about unused functions for ieee80211_crypto.c and
ieee80211_mesh.c for now.
MFC r260039:

Turn off warnings about unused variables for a bunch of files under
contrib/ipfilter.
MFC r260038:

In sys/dev/en/midway.c, #if 0 an unused static function.
MFC r260040:

In sys/dev/mcd/mcd.c, mark the static const COPYRIGHT string as __used,
so it ends up in the object file, and no warnings are emitted about it
being actually unused.
MFC r260042:

Remove superfluous old-style rcsid[] from if_my.c.  There is already an
__FBSDID() at the top of the file.
MFC r260048:

In sys/netgraph/netflow, use __FBSDID() instead of old-style rcs_id[].
MFC r260054:

In sys/dev/tpm/tpm.c, #if 0 an unused static function.
Merge r258690 by mav from head:
  Fix bug introduced at r252226, when udata argument passed to bucket_alloc()
  was used without making sure first that it was really passed for us.

  On some of my systems this bug made user argument passed by ZFS code to
  uma_zalloc_arg() unexpectedly block UMA per-CPU caches for those zones.
MFC r260055:

In sys/dev/usb/wlan/if_urtw.c, #if 0 a static const variable, which has
been unused since r198194.