tiff_ovr_3 fails when creating tiffs with non native endianness

[Even Rouault]

I've added a new creation option to the GTiff driver that enables to set the endianness of the created file. This can also be set with the GDAL_TIFF_ENDIANNESS environement variable. See r14591

I've run the entire autotest suite with GDAL_TIFF_ENDIANNESS=INVERTED and observed that tiff_ovr_3 fails. (I've modified tiff_ovr.py to run with native and inverted endianness so we can exhibit this bug. See r14592)

[Even Rouault]

The reason for the failure was that TIFFWriteEncodedStrip/TIFFWriteEncodedTile can modify the buffer that is passed to them if the endianness of the file is not the native endianness. The solution was to copy the buffer in a temporary buffer before passing it to those functions.

Fixed in trunk in r14596

[Even Rouault]

"Replace tmsize_t by int in previous commit as tmsize_t is not defined in old libtiff headers" in r14597

[Even Rouault]

The fix in trunk was the opportunity to reorganize strip&tile writing, and then it is maybe too intrusive for backporting to 1.5. Closing then.