configure: print warning for old compilers
configure: print warning for old compilers

Try to autodetect the C and C++ compiler and issue a warning when it's
too old to plausibly build io.js.  Emit warnings only because there is
much that can go wrong when trying to invoke a compiler.

PR-URL: https://github.com/iojs/io.js/pull/455
Reviewed-By: Chris Dickinson <38a75c4c4f5646d63b752460df745c5b937b7e58@gmail.com>
Reviewed-By: Rod Vagg <f9f03903429036ef609ed7ca822fddfa76155c29@vagg.org>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node