syntax-check rule to silence -Winclude-next-absolute-path warning

[Bruno Haible]

Does anyone want to contribute a syntax-check rule (in maint.mk) for this?

The full list of header files for which #include "..." is to be avoided is:

alloca.h
arpa_inet.h
assert.h
ctype.h
dirent.h
errno.h
error.h
fcntl.h
fenv.h
float.h
fnmatch.h
getopt.h
glob.h
iconv.h
inttypes.h
langinfo.h
limits.h
locale.h
malloc.h
math.h
monetary.h
netdb.h
net_if.h
netinet_in.h
omp.h
poll.h
pthread.h
pty.h
sched.h
search.h
selinux/selinux.h
signal.h
spawn.h
stdalign.h
stdarg.h
stddef.h
stdint.h
stdio.h
stdlib.h
string.h
strings.h
sysexits.h
sys/file.h
sys/ioctl.h
sys/msg.h
sys/random.h
sys/resource.h
sys/select.h
sys/sem.h
sys/shm.h
sys/socket.h
sys/stat.h
sys/time.h
sys/times.h
sys/types.h
sys/uio.h
sys/utsname.h
sys/wait.h
termios.h
threads.h
time.h
uchar.h
unistd.h
utime.h
utmp.h
wchar.h
wctype.h