Fixes the build issue for compilers without C99 complex type
support as discussed.  Detection uses a configure test because
checking macros and compiler versions seemed too hairy.  Tested on
s390x. 

As a slight safety measure, the patched code uses "<type>
_Complex" instead of "_Complex <type>" as in the examples of the
C99 standard document, just in case there's some odd compiler out
there that requires that specific order (although the standard
demands that any order is allowed).

Ciao

Dominik ^_^  ^_^

-- 

Dominik Vogt
IBM Germany