complex.h

[Marc Glisse <marc dot glisse at inria dot fr>]

Hello,

here is a patch for PR54112. It does 2 things:
* #undef complex after including the system's complex.h
* in C++11, still include the system's complex.h

The C++11 standard says that including complex.h is equivalent to 
including <complex>, with the rationale that a C++ compiler can't parse a 
C99 complex.h header. However, g++, as an extension, handles _Complex, so 
it makes sense to also provide the prototypes for cacos and other C99 
complex math functions.

Tested, no regression.

(Cc: Benjamin, who wrote the header)

2012-07-28  Marc Glisse  <marc.glisse@inria.fr>

        PR libstdc++/54112
	* include/c_compatibility/complex.h: Undefine complex, always
	include system's complex.h if present.
	* testsuite/26_numerics/complex/c99.cc: New testcase.
	* testsuite/17_intro/headers/c++1998/complex.cc: Likewise.

--
Marc Glisse

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