Expand docs, dump config.log on failure, version bump

[dubiousjim]

Made an attempt to document the changes I pushed and you merged recently. Also to give some context about the difference between Rust's (and this package's) interpretation of "host/target" and that of Gnu autotools.

When developing my own package which used this one, I found it helpful to see a dump of config.log if the configure script failed. Proposing that change here too. Am glad to revert it or make it a separate PR if you like.

Finally, bumped the version. Please consider publishing the new version, so that I can publish my own package that relies on these changes.

[dubiousjim]

ping

[lu-zero]

Somehow the notification for this got lost :/

[lu-zero]

I took in the documentation changes, using cat is not going to work on certain targets, but printing on stderr where config.log is might be a good idea.