avoid various seemingly bogus warnings with GCC 14.

i couldn't see any real case for any of these issues. it seems like
the "maybe uninit" checker has gotten worse.

additionally, the "dangling pointer" checker also failing.

apply some warning disables for GCC 12.

*possibly* the one for intel_dp.c is a real bug but it seems very
difficult to be sure (i can't seem to convince myself either way.)

adapt to ${CC_WNO_MAYBE_UNINITIALIZED}

Use ${CC_WNO_MAYBE_UNINITIALIZED} instead of
the older style more complex expressions.

Remove workarounds if they were for a specific
version of gcc < 10.

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.

drm: Dust off module build a little.

Suppress some harmless clang warnings.

build the drmkms modules with -fwrapv too

branches: 1.17.2; 1.17.6;
apply some -Wno- to ignore several new warnings with GCC 10.


ntp: ignore truncation beyond api sizes, and ignore wrongly
guessed underflow

tmux: ignore maybe uninitialised warning for impossible case

libbfd: signed/unsigned variables assigned in the same statement

dri/gallium: -Wno-builtin-declaration-mismatch for u_atomic.c as
it implements backend functions with different in-C-machine but
same-in-real-machine types

libXfont/libXfont2: signed/unsigned variables assigned in the same
statement

i915drm: ignore impossible maybe uninitialised warnings

sysinst: ignore an invalid string truncation issue

branches: 1.16.4;
Provide a global no-packed-address for both gcc and clang

Carry new CWARNFLAGS over to module reachover makefiles.

Forgot these modules existed!

branches: 1.14.2;
convert HAVE_GCC == 7 to HAVE_GCC >= 7.

Bump default value of WARNS for modules from 3 to 5, and
explicitly set WARNS for modules that fail with WARNS=5.

Also, turn on -Wno-missing-noreturn for clang for some files.

At the moment, among ~ 360 modules,
- 2 (lua and zfs) need WARNS=0
- 1 (solaris) needs WARNS=1
- 136 need WARNS=3 (mostly due to sign-compare)
- 4 need WARNS=4
- others can be compiled with WARNS=5

Discussed on tech-kern.

add -Wno-error=int-in-bool-context or -Wno-error=implicit-fallthrough
for various drm files that would be best ignored or upstream fixed.
(could fix savagedrm, no one upstream is that any more.)

Remove some superfluous vestigial `-I.'.

Rework PCI and AGP conditionalization.

- Push drm_pci_set_unique into driver callback.
- Eliminate drm_pci_set_unique_hook.
- Gather all drm_agp_* functions into struct drm_agp_hooks.
- Replace the nonsensical old atomic garbage by serious locking.
- Make drm_agpsupport.c its own module.
- Eliminate NDRMKMS_PCI.
- Use NAGP from "agp.h" only in drm_module.c for horrible hack.
=> See comment in file for rationale.
- Always define CONFIG_PCI=1 and CONFIG_AGP=1.
- Always go through the drm_agp_* function hooks.
- Ifdef out nouveau agp stuff that doesn't go through drm_agp_*
for reasons that I'm too frustrated to figure out tonight.
- pci_iomap no longer automagically does agp_i810_borrow.
=> Use drm_agp_borrow instead.

Make i915drmkms.kmod build again.

branches: 1.8.16; 1.8.18;
consistency with: src/sys/external/bsd/drm2/i915drm/files.i915drmkms
so that we can build again

branches: 1.7.2;
Adjust flags to allow building with clang.

turn on dynamic ldscript creation to handle link set symbol definitions
used in the automatic sysctl creation.

fix build failure.

> /tmp/bracket/build/2014.11.10.22.43.46-i386/src/sys/external/bsd/drm2/include/linux/pci.h:36:20: fatal error: acpica.h: No such file or directory

branches: 1.4.2; 1.4.4;
Rework Intel framebuffer attachment.

Turns out genfb_softc must be at the start of its own device_private,
so we can't have it in the middle of a structure, and certainly can't
have potentially multiple genfbs per graphics device. Failing to do
this is why entering ddb didn't work with an i915drmkms console.

Instead of putting a genfb_softc into each drm_fb_helper, put a
device_t into each drm_fb_helper and create a new intelfb(4) device
for each Intel framebuffer. This will be more flexible, too, in case
we want accelerated framebuffers later on. (XXX Need to adapt the
radeon code, which I'm disabling until that happens to avoid breaking
the build.)

While here, defer disabling VGA, vga_cndetach, and genfb_attach until
we're actually ready to do them all together along with the mode
switch. This should reduce the amount of time during which the
screen is blanked, in case it hangs.

Make it build and boot on my test machines.

Screen blanks on boot on the Ivy Bridge system with

DRM error in cpt_serr_int_handler: PCH transcoder A FIFO underrun

But after that everything is OK. Appears to be an upstream problem.
To investigate...

I think there's a cache flushing issue somewhere -- there are little
display artefacts on my T60.

branches: 1.2.2; 1.2.4; 1.2.6;
Merge riastradh-drm2 to HEAD.

branches: 1.1.2;
file Makefile was initially added on branch riastradh-drm2.