Where possible, QIODevice::peek has been used instead of transactions or instead of using ungetchar() for sequential access devices and seek() for random access devices.
Furthermore:
- RAS format gained the ability of read on sequential devices.
- Removed unused code in XCF (still related to ungetchar and sequential devices).
- These changes should prevent errors like the ones fixed by MR !258
While working on MR !230 I noticed that the options read I entered into several plugins could not be read after reading the image.
**The patch fixes problems reading options in plugins and adds option checking in the readtest.cpp.**
In particular, the reading test does the following additional actions:
- reads options before reading the image;
- compare the options read with the options returned by the reader after reading the image;
- compares the format and size of the returned image with the format and size returned by the reader.
