Fix SPLASHSCREEN_IMAGE handling

This allows a kernel compiled with options:

options SPLASHSCREEN
makeoptions SPLASHSCREEN_IMAGE="path/to/image"

to correctly display the built-in image, which was previously failing to be
initialized by init_main.c. Note that init_main.c was already checking for
makeoptions_SPLASHSCREEN_IMAGE and SPLASHSCREEN_IMAGE inconsistently in two
places, and now it doesn't anymore.

branches: 1.6.42;
Only need to build stbi if options SPLASHSCREEN is defined

Handle splash image generation better.

Include splash with genfb.
splash.o is only included with options SPLASHSCREEN.
splash_image.o target moved to Makefile.kern.inc.

This commit was approved by matt@

branches: 1.3.14; 1.3.32;
- add support for using compressed images as splash images
- retire SPLASHSCREEN_PROGRESS and SPLASHSCREEN_IMAGE options

branches: 1.2.2; 1.2.10; 1.2.16; 1.2.22; 1.2.100; 1.2.106; 1.2.108;
use defparam for SPLASHSCREEN_IMAGE

Import splash screen support.

Do not panic if the splash screen is bigger than the framebuffer

This fixes a kernel crash if the splash screen does not fit inside the
framebuffer. It should probably be truncated (and optionally centered)
instead, but this avoids a panic in the meantime.

Tested on NetBSD/amd64 with a vesa framebuffer.

From Christian Koch (cfkoch@) of EdgeBSD; thanks!

XXX pull-up(s)

branches: 1.12.2; 1.12.14; 1.12.16;
Nat Sloss in PR kern/46516: advance fb pointer by stride, not logical
width of the splash image.

branches: 1.11.4;
%zu for size_t, not %zd

%d -> %zd for size_t printf format

- add support for using compressed images as splash images
- retire SPLASHSCREEN_PROGRESS and SPLASHSCREEN_IMAGE options

branches: 1.8.2; 1.8.4; 1.8.6;
Restore splashscreen support with genfb.
genfb patch from Pierre Pronchery, other small changes to make it
compile by me.

Closes PR kern/42605.

XXX doesnt work in 8bit, probably a cmap issue

branches: 1.7.2;
struct device * -> device_t, no functional changes intended.

branches: 1.6.12;
Backout previous: the license sweep touched these files in error, so
restore the old license.

branches: 1.5.2;
Remove clause 3 and 4 from TNF licenses

branches: 1.4.20;
machine/{bus,cpu,intr}.h -> sys/{bus,cpu,intr}.h

branches: 1.3.8; 1.3.22; 1.3.24; 1.3.28;
Inline UPDATE_INTERVAL macro, it's only used once. Per mrg@'s note
on previous.

Use curcpu() instead of referencing &cpu_info_primary (which is only
defined by a handful of ports).

OK by christos@

branches: 1.1.2; 1.1.10; 1.1.16; 1.1.20; 1.1.22; 1.1.24;
Import splash screen support.

- add support for using compressed images as splash images
- retire SPLASHSCREEN_PROGRESS and SPLASHSCREEN_IMAGE options

branches: 1.4.4; 1.4.6; 1.4.8;
struct device * -> device_t, no functional changes intended.

branches: 1.3.12;
Backout previous: the license sweep touched these files in error, so
restore the old license.

branches: 1.2.2;
Remove clause 3 and 4 from TNF licenses

branches: 1.1.2; 1.1.10; 1.1.14; 1.1.16; 1.1.22; 1.1.76;
Import splash screen support.

branches: 1.6.16;
Clean up splash image build. Print messages when creating files.

Fix build of SPLASHSCREEN without SPLASHSCREEN_IMAGE. Since there is no way
to change ALLFILES by makeoptions, build an empty splash_image.o.

Handle splash image generation better.

branches: 1.3.2;
Forgot RCS ID header.

Include splash with genfb.
splash.o is only included with options SPLASHSCREEN.
splash_image.o target moved to Makefile.kern.inc.

This commit was approved by matt@

Added a new option for embedding a splash screen into kernel.
Add: options SPLASHSCREEN
makeoptions SPLASHSCREEN_IMAGE="path/to/image"
to your config file. So far it will work on amd64 and RPI/RPI2.

This commit was with ideas, help, and OK from jmcneill@.