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 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 r260026:

Disable warning about unused functions for ieee80211_crypto.c and
ieee80211_mesh.c for now.
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.
MFC r260055:

In sys/dev/usb/wlan/if_urtw.c, #if 0 a static const variable, which has
been unused since r198194.
MFC r260056:

In sys/dev/vxge/vxgehal/vxgehal-ring.c, #if 0 an unused static function.
MFC r260057:

In sys/dev/scc, remove unused static function scc_setmreg().  While
here, invoke scc_getmreg() in two more places where it can be used.

Reviewed by:	marcel
MFC r260103:

In sys/amd64/amd64/pmap.c, remove static function pmap_is_current(),
which has been unused since r189415.

Reviewed by:	alc
MFC r260095:

For sys/boot/i386 and sys/boot/pc98, separate flags to be passed
directly to the linker (LD_FLAGS) from flags passed indirectly, via the
compiler driver (LDFLAGS).

This is because several Makefiles under sys/boot/i386 and sys/boot/pc98
use ${LD} directly to link, and the normal LDFLAGS value should not be
used in these cases.
MFC r260104:

For sys/ofed/drivers/infiniband/core/cm.c, disable warning about unused
functions for now.
MFC r260112:

In sys/dev/sound/pci/maestro.c, #if 0 two unused static functions.
[automated] Merge in upstream-github/stable/9