Bug fixes which have already applied on Linux

Fixed:

- liblzma search failure on some linux distributions: Reported in http://www.lightzoneproject.org/lorum/startup-crash-linux-version and http://www.lightzoneproject.org/lorum/lightzone-40-ubuntu-studio-1204
- Improper unit for extraCacheSize: Not reported, but you can see this bug in a startup message, as a negative value like "Allocating -572MB for the image cache."
  - When above fixed, UnsupportedOperationException occurs while tile cache used, e.g. when zooming up an image
- Other minor bugs and warnings

These fixes have already applied on OBS Linux packages.