lensfun lookup of canon s95

[Vladimir Nadvornik]

I am testing hugin 2013.0.0_rc2 with exiv2 0.23.

On an Image from compact camera canon s95 hugin reads the lens name as "(65535)" and the lensfun lookup fails.
Changing lens name to empty string helps. This is a problem for fully automatic workflow, for example with
pto_gen --distortion.

The value comes from Exiv2::lensName print method called at SrcPanoImage.cpp:400

As a workaround I added the lens name "(65535)" to the lensfun database.

I wonder if it can be handled better in hugin, for example by ignoring lens names like "(65535)" or by repeating the lookup with empty lens name in SrcPanoImage::readDistortionFromDB and in other methods.

[tmodes (tmodes)]

Trying to fix in repository.
The problem is that exiv2 does not report consistent strings. For Canon cameras it can contain (65535) or (0) for unknown lenses. For Pentax cams it reports the string "Unknown (0xVAL)". I found this 3 values in a quick test and added it to Hugin to ignore it.
If you found further inconsistencies, please report, so we can add them also.