bsd.own.mk: rename GCC_NO_* to CC_WNO_*

Rename compiler-warning-disable variables from
GCC_NO_warning
to
CC_WNO_warning
where warning is the full warning name as used by the compiler.

GCC_NO_IMPLICIT_FALLTHRU is CC_WNO_IMPLICIT_FALLTHROUGH

Using the convention CC_compilerflag, where compilerflag
is based on the full compiler flag name.

introduce some common variables for use in GCC warning disables:

GCC_NO_FORMAT_TRUNCATION -Wno-format-truncation (GCC 7/8)
GCC_NO_STRINGOP_TRUNCATION -Wno-stringop-truncation (GCC 8)
GCC_NO_STRINGOP_OVERFLOW -Wno-stringop-overflow (GCC 8)
GCC_NO_CAST_FUNCTION_TYPE -Wno-cast-function-type (GCC 8)

use these to turn off warnings for most GCC-8 complaints. many
of these are false positives, most of the real bugs are already
commited, or are yet to come.


we plan to introduce versions of (some?) of these that use the
"-Wno-error=" form, which still displays the warnings but does
not make it an error, and all of the above will be re-considered
as either being "fix me" (warning still displayed) or "warning
is wrong."

branches: 1.15.82;
We only need libutil in native mode.

More programs using efun.

Consistently check ${TOOLCHAIN_MISSING} against "no".

Rework how MAKEVERBOSE operates:

* Don't bother prefixing commands with a line of ${_MKCMD}\
and instead rely upon "make -s". This is less intrusive on
all the Makefiles than the former. Idea from David Laight.

* Rename the variables use to print messages. The scheme now is:
_MKMSG_FOO Run _MKMSG 'foo'
_MKTARGET_FOO Run _MKMSG_FOO ${.TARGET}
From discussion with Alistair Crooks.

support MAKEVERBOSE and use ${HOST_SH}

Now that <bsd.prog.mk> DTRT if HOSTPROG is defined (i.e, it is a no-op),
there's no need to special-case .include-ing it.

* Eliminate the USE_NEW_TOOLCHAIN variable. Instead, split it into
two variables:

TOOLCHAIN_MISSING -- set to "yes" on platforms for which there is
no working in-tree toolchain (hppa, ns32k, sh5, x86_64).

EXTERNAL_TOOLCHAIN -- if defined by the user, points to the root of
an external toolchain (e.g. /usr/local/gnu). This enables the cross-build
framework even for TOOLCHAIN_MISSING platforms.

If TOOLCHAIN_MISSING is set to "yes", MKGDB, MKBFD, and MKGCC are all
unconditionally set to "no", since the bits are not there to build.

If EXTERNAL_TOOLCHAIN is set, MKGCC is unconditionally set to "no",
since the external toolchain's compiler is not in-sync with the
in-tree compiler support components (e.g. libgcc).

* Set MACHINE_CPU much earlier in bsd.own.mk, so that more tests in
that file can use it.

Move check of USE_NEW_TOOLCHAIN so it'll actually be *defined* for a native
crunchgen binary where appropriate.

Use .PATH to find mkskel.sh; formatting cleanup.

When adding something to CPPFLAGS, use +=, not =

If USE_NEW_TOOLCHAIN is defined use objcopy instead of crunchide as it works now.

use CPPFLAGS instead of CFLAGS

branches: 1.3.2;
1) RCSid police
2) Add __RCSIDs where apropriate.
3) WARNS=1, and clean up sources for WARNS=1 (including replacement of
a mktemp with a mkstemp even though it was probably safe...)
4) Some other small cosmetic changes

local changes; install into /usr/bin, deal with sh warnings, deal with obj.MACHINE, etc.

branches: 1.1.1;
Initial revision