bug#22357: grep -f huge memory usage

[Jaroslav Skarvada]

Using the files [1], [2] (around 1.4 MB each) and running the
following command:

$ grep -v -f file1 file2

quickly consumes all of my memory (16 GB) and exits with memory
exhausted error. I have reports that it behave the same on machine
with 180 GB RAM. Well, -F should be used as there are no regexes,
but the same worked with grep-2.5.1 and consumed only cca 0.5 GB of RAM.
Maybe there is a room for optimization

thanks & regards

Jaroslav

[1] https://jskarvad.fedorapeople.org/grep/file1
[2] https://jskarvad.fedorapeople.org/grep/file2