[PyQt] QtX11Info cfgtest fails with Qt 5.1

[Dmitry Shachnev]

Hi,

QtX11Info test is tried with Qt ≥ 5.1, but it fails with 5.1.1 (as in
Debian unstable):

cfgtest_QtX11Extras.cpp: In function 'int main(int, char**)':
cfgtest_QtX11Extras.cpp:5:5: error: 'isPlatformX11' is not a member of
'QX11Info'
     QX11Info::isPlatformX11();
     ^
make[1]: *** [cfgtest_QtX11Extras.o] Error 1

That function was introduced in Qt 5.2. Can it please be fixed to
support 5.1 as well?

I think qx11info_x11.sip will need some adjustment as well.

--
Dmitry Shachnev