Support for UFS1 extended attributes in GENERIC and GENERIC-like kernels

This change just brings UFS1 extended attribute *support* in the kernel,
extended attributes are not enabled unless three conditions are met:
1) filesystem is UFS1 (newfs -O1)
2) .attribute/system and .attribute/user directories are created at fs root
3) filesystem is mounted with -o extattr

Some GENERIC kernels are obviously memory constrained, the extended
attributes options were not enabled for them, but just added commented out.
(kernel were considered memory constrained if QUOTA option was disabled)
restore previous functionality, and add what we need with -t <template>
add -t to mkldscript
If the internals are not explicitly requested, use #include_next to pick
up the system version. <locale> from libc++ requires this and is used by
src/tools/elftosb2.
apply several changes from intelfb.c revs 1.7 through 1.9:
 - provide a setmode callback for genfb
 - add a pmf shutdown handler to switch genfb into polling mode
 - no need to call drm_fb_helper_set_config after genfb attaches,
   as the setmode callback is called by genfb_attach
Add A20 HDMI audio support. Basically the same as A31, except we need to use dedicated DMA mode here (A31 DMA controller only supports "normal DMA" mode).
add awinhdmiaudio
Change the order of arguments to check_ids, placing the two file names
adjacent to each other.  Also add a comment explaining the "start"
argument and the "SKIP" special value.
sync both instances of the ldscript.
Fix tab/space inconsistency in comment.