Let --trace have arguments.

* src/getargs.h (enum trace_e): New.
* src/getargs.c (trace_args, trace_types, trace_argmatch): New.
(long_options, short_options): --trace/-T takes an optional
argument.
Change all the uses of trace_flag to reflect the new flags.
* tests/sets.at (Firsts, Nullable, Broken Closure): Use --trace=sets.
Strengthen `stage' portability.
* m4/stage.m4 (BISON_PREREQ_STAGE): New.
* configure.in: Use it.
Don't check for malloc.h and sys/times.h.
* src/system.h: Include them when appropriate.
* src/main.c (stage): Compile only when mallinfo, struct mallinfo,
times and struct tms are available.

m4/warning.m4

@@ -1,4 +1,25 @@
-AC_DEFUN(BISON_WARNING,
+# Finding valid warning flags for the C Compiler.           -*-Autoconf-*-
+#
+# Copyright (C) 2001, 2002 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+# 02111-1307  USA
+
+# serial 1
+
+AC_DEFUN([BISON_WARNING],
 [AC_MSG_CHECKING(whether compiler accepts $1)
 AC_SUBST(WARNING_CFLAGS)
 ac_save_CFLAGS="$CFLAGS"