Translates '.' in host triples.

configure maps -'s in host triples to _'s in order to create variables of
the form $CFG_FOO_${triple}. The standard triple for Illumos/Smartos is
'*-sun-solaris2.11', and the '.' isn't legal.

This commit adds mapping for . -> _

The standard illumos/smartos host triples are '*-sun-solaris2.11', which
unlike the triples currently supported contains a
Initial platform config for Illumos/SmartOS