* configure.tgt (i[3456]86-*-sysv4.2*, i[3456]86-*-sysv4*,

i[3456]86-*-sysv5*, i[3456]86-*-sco3.2v5*): Remove.  These are all
handled fine by i[3456]86-*sco* and i[3456]86-sysv*.
* config/i386/i386sco5.mt, config/i386/i386v4.mt,
config/i386/i386v42mp.mt: Removed.