[ptx] Error checking in TIFF routines

[dmg]

Some people have reported errors in panotools due to lack of LZW
support in their library. I followed up on this problem and discovered
that panotools is very optimistic when using libTIFF routines: it
rarely checks for return errors code. This means that if there is any
disk error panotools will happily continue processing the file, and of
course no valid output is created.

I just committed some changes that attempt to make panotools more
resilient to these errors. 

* I added an error handler to report libTIFF errors. This means that
  libTIFF will now use the panotools error handling routine
  (PrintError).

* I have checked the return value of  every TIFFWriteScanline. If
  there is an error it reports back the message and aborts the
  operation.

The side effect of these changes is that if the library does not
support LZW an error message is reported and PTmender stop and reports
the error.



--
Daniel M. German
http://turingmachine.org/
http://silvernegative.com/
dmg (at) uvic (dot) ca
replace (at) with @ and (dot) with .