winemp3.acm: link to system libmpg123.so

[Robert Förster]

im getting undefined references to mpg123_feedseek.
im on amd64, building a 32 bit wine, so of course i have a 32 bit lib of 
mpg123 around, which however seems to export mpg123_feedseek_64 instead.
could that be covered too please? (i have reports that this is happening on 
plain x86 boxes too.)

Robert