xzgrep: incomplete results on larger files

[Stefan Ehmann]

I observed the following behavior on 10.1-BETA1 r271683M (amd64):

xzgrep doesn't search the complete file:
$ seq 10000 | xz > seq.xz
$ xzgrep -c . seq.xz
6775

Using regular grep works as expected:
$ xzcat seq.xz | grep -c .
10000

Processing seems to stop after 32KB (uncompressed).