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

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

Our awk does not implement the ARGIND variable, so we were attempting
to parse the binary .kld file as a list of symbols. Fix this by
simply deleting the unwanted argument from the ARGV[] array instead
of trying to skip over it.

Respect setting of NM to allow cross-building.

Only use POSIX Awk features.

Eliminate the use of commons in the kernel and modules,
simplifying the module linking process and eliminating the risks
associated with doubly-defined variables.

Cases where commons were legitimately used (detection of
compiled-in subsystems) have been converted to use sysinits, and
any new code should use this or an equivalent practice as a
matter of course.

Modules can override this behaviour by substituting -fno-common
out of ${CFLAGS} in cases where commons are necessary
(eg. third-party object modules). Commons will be resolved and
allocated space when the kld is linked as part of the module
build process, so they will not pose a risk to the kernel or
other modules.

Provide a mechanism for controlling the export of symbols from
the module namespace. The EXPORT_SYMS variable may be set in the
Makefile to NO (export no symbols), a list of symbols to export,
or the name of a file containing a newline-seperated list of
symbols to be exported. Non-exported symbols are converted to
local symbols. If EXPORT_SYMS is not set, all global symbols are
currently exported. This behaviour is expected to change (to
exporting no symbols) once modules have been converted.

Reviewed by: peter (in principle)
Obtained from: green (kmod_syms.awk)