grep: fix -x -v with certain pattern orders

grep: fix -x -v with certain pattern orders

We found out that busybox -x -v is a bit broken:

ari@ari-thinkpad:~/busybox$ echo '  aa bb cc' | ./busybox grep -x -e 'aa.*' -e '.*bb.*'
  aa bb cc
ari@ari-thinkpad:~/busybox$ echo '  aa bb cc' | ./busybox grep -x -v -e 'aa.*' -e '.*bb.*'
ari@ari-thinkpad:~/busybox$ echo '  aa bb cc' | ./busybox grep -x -e '.*aa.*' -e 'bb.*'
  aa bb cc
ari@ari-thinkpad:~/busybox$ echo '  aa bb cc' | ./busybox grep -x -v -e '.*aa.*' -e 'bb.*'
  aa bb cc

Last one is wrong.

This patch fixes the issue by making sure that the variable 'found'
never makes a transition from 1 to 0, as this would mean that
grep previously found a match on this input line.

Signed-off-by: Ari Sundholm <ari@tuxera.com>
Signed-off-by: Niko Vähäsarja <niko@tuxera.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>