Shut up warnings for setgroups() on Linux -- you have to #include
<grp.h> it seems. This requires yet another configure test.
diff --git a/configure.in b/configure.in
index c2d617e..ed8698a 100644
--- a/configure.in
+++ b/configure.in
@@ -499,7 +499,7 @@
# checks for header files
AC_HEADER_STDC
-AC_CHECK_HEADERS(dlfcn.h fcntl.h limits.h langinfo.h locale.h \
+AC_CHECK_HEADERS(dlfcn.h fcntl.h grp.h limits.h langinfo.h locale.h \
ncurses.h poll.h pthread.h \
signal.h stdarg.h stddef.h stdlib.h thread.h unistd.h utime.h termios.h \
sys/audioio.h sys/file.h sys/lock.h sys/modem.h db_185.h db.h \