[libpng15] Fixes for C++ compilation using g++ When libpng source is compiled

    using g++. The compiler imposes C++ rules on the C source; thus it
    is desireable to make the source work with either C or C++ rules
    without throwing away useful error information.  This change adds
    png_voidcast to allow C semantic (void*) cases or the corresponding
    C++ static_cast operation, as appropriate.
6 files changed