missing const it PQexscapeBytea/PQunescapeBytea in 7.3b3

Hi,

I just discovered, that there is missing a const when passing a buffer to 
PQescapeBytea and PQunescapeBytea. I fixed it and tried to create a usable 
diff (I'm not so familar to diff).

Tommi


(resent with the right identity)