add gcc 14 support.

Create a new header lwp_private.h to contain _lwp_getprivate_fast,
_lwp_gettcb_fast, _lwp_settcb and remove them from mcontext.h, so that:
1. we don't need special hacks to hide them
2. we can include <lwp.h> where needed to get the necessary prototypes
without redefining them locally.

Undo previous lwp.h change.

Split __lwp_getprivate_fast and __lwp_*tcb from mcontext.h into a separate
lwp.h file.

distrib/sets/lists: Add a blank comment line between RCS id and body.

This serves as a buffer between RCS id changes and other changes to
the set lists, in an attempt to reduce the pain of merge conflicts
around mass set list changes.

No functional change intended.

branches: 1.12.2;
distrib/lists/sets/comp: Add gcc=12 obsolete entries for gcc-10/*.h.

mark all previously gcc=9 files as obsolete.

also mark a bunch of obsolete gcc headers as "comp-obsolete" "set".

should fix a 'postinstall fix obsolete' issue reported by uwe@.

more updates for sets and GCC 12

- renable sanitizer, add new shlib versions, enable tsan for arm64,
including moving some stuff into the per-cpu/arch dir from 'mi'.
- fix mips64, 68k, and ia64
- mark many any-gcc-version things just as "gcc" and remove dups
- mark many gcc=9 only things as obsolete
- mark many gcc=10 only things as obsolete with gcc=12 (more could
be done here.)

various updates for GCC 10 support. remove dead gcc7/8 support
and properly mark obsolete files in gcc9/gcc10.

testing on amd64 and shark for GCC 9, and many platforms for GCC 10,
(though not arm yet.)

mostly support GCC 9 builds. some what tested with GCC 9 but
tested to not break GCC 8 builds for x86, arm*, vax, and sparc*.

gcc 8 set lists updates. i don't appear to have broken gcc 7 builds
but i only tested a couple of them.

add basic gcc-7 support in sets lists and filesystem. mips gained
a header. assumes it's otherwise mostly the same as gcc-7.

- mark gcc=5 files obsolete
- make includes always available, not only when gcccmds
- mark files obsolete consistently

branches: 1.4.2; 1.4.4;
minimal basic support for ia64 and gcc6. i am not sure about the
bp part of the GetPcSpBp() port, cherry please look :-)

Add fenv.h for ia64, imported from FreeBSD, compile tested only.

branches: 1.2.2;
Tag cleanup: if the last column contains 'obsolete', the one before should too.

branches: 1.1.2;
PR port-ia64/51261

Changes for ia64