[gdal-dev] support for libpng 1.5.0

[Ben Discoe]

I tried building GDAL 1.7.3 this evening and found that it did not support the new libpng 1.5.0.
I also looked at the archive for GDAL 1.8.0 RC2, and it seems to have the same code in question.

The changes are small, just a few like this:

<    VSIFFlushL( (png_FILE_p) png_get_io_ptr(png_ptr->io_ptr) );
>    VSIFFlushL( (png_FILE_p) png_get_io_ptr(png_ptr) );

And one like this:

<    jmp_buf* psSetJmpContext = (jmp_buf*) png_ptr->error_ptr;
>    jmp_buf* psSetJmpContext = (jmp_buf*) png_get_error_ptr(png_ptr);

On a personal note, it feels good to be back here again, building GDAL.  I started with GDAL back at the dawn of time, mid-2000, and it's been a long, happy relationship.

-Ben