Migration to version 0.3

The Packet IO Engine v0.3 has a major change of its library and header file naming. Previously, we had used "ps.h" and/or "pslib.h" for the main header file and "-lps" for the library linking. The name "ps" is somewhat too general because the Packet IO Engine does not include all of other user-level implementations of PacketShader, but only the Packet IO driver and the reference implementation of user-level API.

To eliminate future confusions, we have decided to change the library name to "psio", and to use "psio.h" / "-lpsio" accordingly.

The API function prototypes were not changed and the structure definitions such as struct ps_chunk and struct ps_device are compatible with existing codes in the source level. The names of several constants have been changed: MAX_PACKET_SIZE to PS_MAX_PACKET_SIZE, MAX_CHUNK_SIZE to PS_MAX_CHUNK_SIZE, MAX_DEVICES to PS_MAX_DEVICES, and so on.