Don't save deleted lines to (default) register.

Previously, after deleting lines, they could be restored from the
default register, e.g.,

$ ed -p '*'
*a
hello
world
.
*1d
*,p
world
*<t0
*,p
hello
world
*

Since this adds significant overhead, it has been disabled by default.
To restore the old behavior, define CFLAGS macro WANT_ED_REGISTER_DELETE,
e.g.,

./configure --enable-all-extensions CFLAGS=-DWANT_ED_REGISTER_DELETE

configure.ac

@@ -209,9 +209,7 @@ AM_GNU_GETTEXT_VERSION([0.21])
 AX_CHECK_OPENSSL([ac_cv_have_openssl='yes'])
 
 AC_FUNC_FORK
-AC_FUNC_VFORK
 AC_FUNC_FSEEKO
-AC_PROG_GCC_TRADITIONAL
 
 # NB: malloc.c from GNU libc is problematic, e.g., for cross-compiling
 AC_FUNC_MALLOC

src/exec.c

@@ -441,15 +441,15 @@ d_cmd (ed_buffer_t *ed)
   if ((status = is_valid_range (ed->state->dot, ed->state->dot, ed)) < 0)
     return status;
 
-#ifdef WANT_ED_REGISTER
+#ifdef WANT_ED_REGISTER_DELETE
   /* Save deleted lines in default register. */
   ed->core->regbuf->io_f |= REGISTER_WRITE;
   ed->core->regbuf->write_idx = REGBUF_MAX - 1;
 #endif
   COMMAND_SUFFIX (ed->display->io_f, ed);
   if (!ed->exec->global)
     reset_undo_queue (ed);
-#ifdef WANT_ED_REGISTER
+#ifdef WANT_ED_REGISTER_DELETE
   if ((status = append_to_register (ed->exec->region->start,
                                    ed->exec->region->end, 0, ed)) < 0)
     return status;