* src/gdbmshell.c (command_type): Change initializer.
(gdbmshell_run): Initialize the .len member.

* doc/gdbm.texi: Document the perror command.
* src/gdbmshell.c: New command: perror.
(run_command): In timing mode, print also user and system CPU times.
Print traces on stderr.
* src/gdbmtool.c: New options: -t (--trace) and -T (--timing).

* src/gdbmshell.c (run_command): Print command trace if requested.
Prefix timing info with the name of the command.
* src/var.c: New variable: trace.

* src/gdbmshell.c (run_command): Print real execution time, if
the "timing" variable is set.
* src/var.c: New boolean variable: timing

Boolean errorexit controls whether script terminates upon first
erroneous return from run_command or its derivatives.  The variable
can be set only in non-interactive mode.

errormask is a comma-delimited list of GDBM error codes that are
masked, i.e. that won't trigger a diagnostic message if they occur.
* src/gdbmshell.c (all handlers): Return integer value indicating
success (0) or failure (!0).
* src/gdbmtool.h (input_context_drain): New function.
(run_last_command): Return integer.
* src/gram.y: abort if run_command returns error and "errorexit" is
set.
* src/input-argv.c (instream_argv_read): Bugfix.
* src/lex.l (input_context_drain): New function.
* src/var.c: New variables: errorexit and errormask.

* src/gdbmshell.c: Revise error messages.  Use dberror where
appropriate.
* src/gdbmtool.h (dberror): New proto.
* src/gram.y (dberror): New function.

* src/Makefile.am (libgdbmapp_a_SOURCES): Add input-std.c
* src/gdbmshell.c (input_history_begin): Improve diagnostic message.
* src/gdbmtool.c (instream_default_create): New define.
(gdbmtool_init): Use instream_default_create.
* src/gdbmtool.h [WITH_READLINE] (instream_readline_create_: New proto.
(input_stream_name): New proto.
* src/input-rl.c (instream_stdin_create): Rename to instream_readline_create.
Fall back to instream_stdin_create if stdin is not connected to a tty.
* src/lex.l (input_stream_name): New function.