lint: clean up

lint: rename symt_t to symbol_kind

It was confusing to have two kinds of "symbol type" (s_type and s_symt),
so rename all related identifiers to be more distinctive.

No functional change.

lint: on lint itself, disable query for const variables again

It suffixes to perform this check on demand.

lint: clean up redundant const from parameters and local variables

These were leftovers from splitting large functions into smaller
functions, to ensure that variables were not unintentionally reassigned.
Those refactorings are finished, and the extra help from the compiler is
no longer necessary.

No binary change.

lint: disable -ftrapv for vax

When compiling lint1/cgram.c:
during RTL pass: postreload
cgram.c: In function 'yyparse':
cgram.c:5873:1: internal compiler error: in reload_combine_note_use,
at postreload.c:1534

lint: enable more lint warnings for its own source code

PR 56789: avoid -ftrapv for alpha, it triggers a gcc error.
OK: rillig

lint: ensure that lint itself compiles without lint warnings

It would be a pity if lint didn't even survive its own style checks.

lint: fix undefined behavior on enum overflow (since 1995)

GCC had optimized the check away, due to the obvious integer overflow 'x
- 1 == INT_MAX'. To prevent further bugs like this, compile with
-ftrapv.

lint: clean up memory management for string buffers

There is no reason to duplicate all the work that is already done by the
memory allocator.

No functional change.

lint: enable memory debugging

Filling deallocated memory with 0x00 may hide errors, so rather fill
with 0xA5.

While this doesn't change anything about the test about the assertion
failure after a do-while loop (see t_integration.sh, test case
assertion_failures), it may detect other similar bugs earlier.

lint: drop compatibility with C90

Since tools/README 1.5 from 2022-02-03, the tools no longer need to be
compatible with C90, they may now use C99 features. Lint had used
<stdbool.h> and snprintf already.

No functional change.

lint: enter full C90 compatibility mode

The C99 comment in tree.c:3468 has been there since 2017-03-06, without
anyone complaining that their compiler would not handle it.

Strangely, running GCC 10.3.0 in '-std=c90' mode does not complain about
declarations after statements, '-Wdeclaration-after-statement' is needed
separately.

No functional change.

lint: move all declarations above statements

All code that is used by src/tools is supposed to be compatible with C90.

No functional change.

lint: clean gcov files for lint2 and xlint as well

lint: remove WARNS=3, falling back to the default WARNS=5

It's strange that GCC does not warn about the nonliteral format strings
in lint1/err.c, lint2/msg.c and lint2/read.c, despite -Wformat=2, but
Clang does.

Make mips64e[bl] check more generic.

branches: 1.12.6; 1.12.12;
for mips64*, use mips64 subdir, otherwise use $MACHINE_ARCH if exists,
or $MACHINE_CPU. idea from dennis.c.ferguson@gmail.com in PR#43021.

Merge from matt-nb5-mips64
Teach lint about mips64

Compile lint with WARNS=3.
Currently there are too many -Wsign-compare issues for WARNS=4.

branches: 1.9.44; 1.9.48;
Need <bsd.own.mk> to use ${MACHINE_CPU}.

On m68000, we need different target parameters than on m68k,
because "long double" is a different size on m68000.

* Move stuff shared between lint1 and lint2 to the new common/ directory.
* Move the arch/ directory out of lint1/ into the top-level.

Major overhaul of src/tools and host toolchain. Summary of changes:

* Rewrite src/tools Make logic to work like the rest of the tree wrt
"dependall" and "install". The old "make build" hack is gone.

* Remove the MKTOOLS logic. This was linked to the "make build" hack,
and was only needed because TOOLDIR originally had no writable default.

* Redo the GNU configure/make logic to make it fit reasonably in a
BSD make wrapper. Use new ${.ALLTARGETS} variable to scan for
targets in $(srcdir), and mark them with .MADE: to prevent rebuilding.

* Only build cross tools in src/tools; remove some messy logic in
src/usr.* and src/gnu/usr.* that would do target filename rewriting
(improves consistency and readability).

* Add the ability to build cross gdb at tool build time by setting
MKCROSSGDB (default no) to "yes" in mk.conf.

* Add src/tools/groff and set up paths to work with this cross groff.

Give host tool builds better control over the HOST_CPPFLAGS.

Move CPPFLAGS addition for lint1/arch to Makefile.inc so each subdir will
pick them up

WARNSify

Don't use " inside an '.if exists()'

branches: 1.1.2;
add Makefile.inc to turn off WARNS, and use it