Fix #4: FLI_SS2 writes lines with packet count >= 0x8000.
Fix #4: FLI_SS2 writes lines with packet count >= 0x8000.

This fixes commit 6971785f97cea839e9250c0692751fe8bc952fc6.

The bug allows lines with packet counts between 0x8000 and 0xFFFF to
be written, which would be interpreted as either a "skip lines" or a
"write last byte" operation.

wangds/libflic,wangds/libflic