glmark2 fails to build with gcc 4.8+

[Bernhard Rosenkraenzer]

glmark2 fails to build with gcc 4.8 because the "%s"m construct in the internal png.h copy is misinterpreted as a C++11 string literal.

[Jesse Barker (jesse-barker)]

Silly question: why is C code being interpreted as C++11 at all?

[Bernhard Rosenkraenzer (berolinux)]

Still broken in current git://git.linaro.org/people/jessebarker/glmark2

It's being interpreted as C++11 because it's being included from a C++ file -- glmark2/android/jni/src/image-reader.cpp

Of course just using system libpng may be better either way.

[Bernhard Rosenkraenzer (berolinux)]

I've pushed a fix to the git repository, chances are you want to add it to the bzr repository as well