Fix support clang when we use autotools

[kjunichi]

Hello.

When I build http://www.geocities.jp/kosako3/oniguruma/archive/onig-5.9.5.tar.gz using qrintf clang as CC command, I notice that ./configure miss understood C89 option.

This patch solves it.

Sorry, I can't explain easyliy in English.

I worte blog article at http://kjunichi.cocolog-nifty.com/misc/2015/07/qrintfclangauto.html

thank you.

by the way, I heard rebuildfm 99 It was very interesting.

[kazuho]

Thank you for the PR. Will leave comments in-line.

[kazuho]

Aside from the in-line comments, what is the expected behavior if more than one source files are specified together with -c option? (e.g. -c foo.c bar.c).

I would appreciate it if you could describe the expected behavior and confirm that the PR works correspondingly.

[kjunichi]

Thank you for your comment.

The rewrite should not be limited to .c
Yes, you are right. I have no idea about that cases.

what is the expected behavior if more than one source files are specified together with -c option?
I expected foo.o,bar.o.

Now I think that It's better to change my logic.

Like this :
all processing is done,then add the following logic.
mv .o .o
and We don't need .i .
so rm .i

I think the filenames can be saved using hash table.

What do you think?

thank you.