Tiny bugfixes

* AUTHORS: add e-mail address
* ChangeLog: update
* TODO: mention curl_easy_getinfo
* bootstrap.conf: add gitlog-to-changelog
* build-aux/.gitignore: ignore gitlog-to-changelog
* configure.ac: bump interface, use curl-config
* doc/guile-curl.texi: try to use xref at end of sentence
* src/Makefile.am: user curl-config flags
* src/func.c: bad printf format