Don't need to emit an empty fixed block when changing parameters.
Don't need to emit an empty fixed block when changing parameters.

gzsetparams() was using Z_PARTIAL_FLUSH when it could use Z_BLOCK
instead. This commit uses Z_BLOCK, which avoids emitting an
unnecessary ten bits into the stream.

Streamlet/ZLibWrap,Streamlet/ZLibWrap,Streamlet/ZLibWrap,Streamlet/ZLibWrap,Streamlet/ZLibWrap