[Patch] Fix ac_c99_complex configury

[Gabriel Dos Reis]

Paolo Carlini <pcarlini@suse.de> writes:

| Gabriel Dos Reis wrote:
| 
| >Paolo Carlini <pcarlini@suse.de> writes:
| >
| >| Another, more serious, tought I entertained during the last weeks,
| >| actually, is whether we could *finally* remove the include/backward
| >| stuff! I believe that for 4.1 would be absolutely *correct* wrt our
| >| deprecation/removal policy.
| >
| >In theory it would be in line with our policy; however in practice it
| >would be a disaster.  This stuff is even described in the C++ standard
| >(under the deprecated heading I agree) and there are still people
| >using it.
| >
| Are you *really* *sure* the standard describes such headers?!? I don't
| think so.

The <strstream> header is certainly described in §D.7.1. 
Old iostreams are in §D.6, and the common practice is that old
iostream means <iostream.h>.  Now, I don't see much reasons to keep
those <xxx.h> files remove others, as they have been in the legacy
base.  I would say that if we don't have maintanance burden with them,
then we should keep them.  

-- Gaby