[SV 62118] Correctly handle -f- options on re-exec

[SV 62118] Correctly handle -f- options on re-exec

The -f, -file, and --makefile options were not properly handled when
re-exec'ing due to makefile updates.  This problem, plus a patch and
tests, was reported by Dmitry Goncharov <dgoncharov@users.sf.net>.

While examining this I found another bug: after re-exec we forgot the
batch file was temporary and never deleted it.

I decided to fix all these problems at once using a different fix
than Dmitry's: I created a new internal-only command-line option,
--temp-stdin.  When reconstructing the make options for a re-exec,
replace the -f/--file/--makefile option that reads from stdin with
--temp-stdin=<filename> so that the re-exec'd version of make knows
it's a temporary batch file and will delete it.

We no longer need to add the -o options because the re-exec'd make
knows this is a temporary makefile and treats it as such.

To simplify, replace the --file and --makefile options taking a
filename, with just -f<filename> on re-exec.

Some examples of the rewrite:

  User command line               Re-exec command line
  -----------------               --------------------
  -f-                             --temp-stdin=<batch>
  --file -                        --temp-stdin=<batch>
  -f - --makefile a.mk            --temp-stdin=<batch> -fa.mk
  --file=a.mk                     -fa.mk
  -fa.mk                          -fa.mk
  -Rf a.mk                        -Rf a.mk
  -Rf-                            -R --temp-stdin=<batch>

* src/main.c (stdin_offset): Remember the offset into the makefiles
list of the batch file read from stdin.  Remove stdin_nm.
(struct command_switch): Create a new --temp-stdin option, which
also updates the makefiles list.
(main): Add the temporary filename to the string cache.
Move the tempfile handling after checking makefile arguments for "-"
so that files provided via --temp-stdin are also handled specially.
When rewriting re-exec options, we may need one more than we had
originally so create a new argv list.  Walk through the original
list and convert it to the new list, following the above process.
(decode_switches): Set the stdin_offset flag if we see --temp-stdin.
* tests/scripts/options/dash-f: Add many more tests, provided by
Dmitry Goncharov <dgoncharov@users.sf.net>.