MinGW: C++11 perfect forwarding support is broken

[David Ostrovsky]

So we have weird breakage on MinGW:

in configure phase i686-w64-mingw32-g++ reports back success for that check:

configure:15247: checking whether ccache i686-w64-mingw32-g++ supports 
C++11 perfect forwarding
configure:15275: ccache i686-w64-mingw32-g++ -c  -std=gnu++0x 
conftest.cpp >&5
configure:15275: $? = 0
configure:15288: result: yes

setting HAVE_CXX11_PERFECT_FORWARDING to 1
and then failing in compile phase with the question: what's that [1].

Workaround for now is uncomment export lines in configure.ac, then it s 
happy again [2]

Environment:

newest OpenSUSE,
david at numpty>i686-w64-mingw32-g++ --version
i686-w64-mingw32-g++ (GCC) 4.7.2

[1] https://ci.idaia.de/job/LO-Mingw64/142/console
[2] https://ci.idaia.de/job/LO-Mingw64/151/console

David