escape130: The minimum read in and after decode_skip_count() is 4 bits.

escape130: The minimum read in and after decode_skip_count() is 4 bits.
Thus we can check for 4 being available.
If the next block is skiped we need 4 bits to encode the skip. If the
next block is not skiped then we need 1 bit for the skip code and
at least 3 bits for the block.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>