prog: allow arbitrary long lines in serialized programs
prog: allow arbitrary long lines in serialized programs

We use bufio.Scanner and it has mandatory limit on line length.
The file system tests (sys/linux/test/syz_mount_image_*) has
very long lines (megabytes).
Remove the restriction on line length.

google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller