Description of problem:
When option -F is used, screen contents are cleared (resp. moved up) even for files that do not fit on the screen.

Version-Release number of selected component (if applicable):
less-436-13.fc15.x86_64

How reproducible:
Always.

Steps to Reproduce:
1. less -F /var/log/Xorg.0.log
2. press q
3. 
  
Actual results:
Old screen contents moved up, parts of the X log remain on the screen.

Expected results:
Screen contents unchanged/restored after exiting less.

Additional info:
For small files, less with -F should behave like cat, but for large files, it should behave as if -F was not given.