configure.ac: ignore CR after version numbers

Ignore everything after the version numbers in LIBCURL_VERSION and
LIBCURL_VERSION_NUM to ged rid of the extra CR character.
This makes tests 1022 and 1023 pass on Linux with a CRLF checkout.

Ref: https://github.com/curl/curl/pull/1344#issuecomment-289243166
Closes https://github.com/curl/curl/pull/1422