remove llvm-clang artefacts in more places
some basic LLVM+clang (with “ccc” driver example) support
support arc4random.c in build but not src dir, too
check return value of unlink(2) when trying to remove an existing HISTFILE,
since mksh(1) did go into an infinite loop if that fails first

bug spotted, initial patch and help drafting a test case
From: Decklin Foster <decklin@red-bean.com>

note there are more instances of unlink(2) and others (like chmod(2), as
spotted by flawfinder) which aren’t checked… but at least the other case
of unlink(2) use in histrap.c doesn’t cause any trouble (I think)
fix HP aCC compiler version identification
libc strlfun.c:
• fix file description, history, etc.
• require <stddef.h> for portable size_t declaration (if ! kernel, bootloader)
• mention why we do _not_ include <string.h> (for building on obsd/mbsd)
• sync RCSID definition with that of mksh (more portable)
• fix strlcat description
• sync strlcpy obsd rcsid and licence header with obsd-current
  (their code change 1.10→1.11 was something we already did)
• use “does not”, not “doesn’t”
• make it easier to produce wcslfun.c

libc wcslfun.c:
• sync with strlfun.c (much easier now)

mksh strlcpy.c:
• sync with strlfun.c (in comments, mostly)

no binary changes
NetBSD® 3.0_STABLE is a tad picky about the UTF-8 locale’s naming…
reverse the sense of check for en_US.UTF-8 vs en_US.utf8:
the latter is required by HP-sUX, okay, and apparently the
preferred one by glibc (GNU libdrepper?), but breaks on al-
most all other systems I have access to (Slowlaris, Midnight
DragonFly NetBSD, Darwin, at least)
dump the perl $^O string in the logs… all Debian GNU/kFreeBSD developers
I can ping right now “need to refresh their keys on io/asdfasdf” or have
their machines unreachable… and I lost my VM to fsck recently (remember)
gcc -v also accepts a file argument, and 'diet gcc -v' croaks, so…
sync with openbsd: only the RCS IDs, because the changed code in
question either does not exist in mksh (lex.c) or refers to the
only “feature” we do not pull, GNU bash-like $PS1 (main.c)
Debian GNU/kFreeBSD $^O value, 10x tarzeau
add another corner case of here documents, which bash and zsh pass
inspired by:
20:14⎜«twkm:#ksh» $ unset foo ; read -u10 foo 10<<< bar ; echo $foo
which works in ksh93 (whose fd>9-support is still incomplete though)
… one more regression test we pass…
• hd <<< bar
  → like bash, ksh93, zsh
• hd <<< #bar
  → like zsh (bash, ksh93: syntax error)
• hd <<<
  → like hd <<< '' (bash, ksh93, zsh: syntax error)
• bump NUFILE and FDBASE, allowing for more than 10 fds used by scripts
• change the code to accept more than a single digit for an fd
remove a line which accidentally got committed, oops
limit fd usage – at least ULTRIX doesn’t cope
let’s find sizer on OSF/1 if it’s not in the PATH
no UTF-8 locales on OSF/1 V5.1B, either
• remove bizarre test constraint
• make a test succeed on Tru64, whose cat likes to output
  │Successful
  │cat: output error
  on this test case