Fix reading ROI files
Fix reading ROI files

- Checks the return value of fopen when opening the ROI file. Fixes
  a segfault when the file cannot be opened.
- Check that the width and height are positive. Fixes reading past the
  end of the delta QP array in kvz_set_lcu_lambda_and_qp.
- Check for overflow in width * height. Fixes an overflow resulting in
  a segfault.
- Properly check that fscanf succeeds. Fixes silently accepting ROI
  files that are too short.
- Properly close the FILE pointer.

ultravideo/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar