Improve "const correctness"

[elfring]

Would you like to apply the advices from the article
"http://en.wikipedia.org/wiki/Const_correctness" to
your sources?
I suggest to add the key word "const" to the type
specifiers for parameters like the following.
- filename (function "ZCombSeeImage")

http://cvs.sourceforge.net/viewcvs.py/panotools/libpano/ZComb.h?rev=1.1&view=markup

- fname (functions ".+BufImage", "FindFile")
  src (functions "CopyImageData", "merge",
"cutTheFrame", ...)
  from (function "CopyPosition")
  im1, im2 (functions "HaveEqualSize", "PositionCmp")
  r (function "CropImage")

http://cvs.sourceforge.net/viewcvs.py/panotools/libpano/filter.h?rev=1.11&view=markup