RELEASE-NOTES: fixed typo
runtests.pl: verify specified test cases

To better allow arguments like "1 to 9999" without flooding the terminal
with error messages, the given test cases range is now checked and only
test numbers with existing files are actually run.
rtsp: parse "Session:" header properly

The parser skipped the initial letter, which presumably often is
whitespace but doesn't have to be.

Reported-by: Mike Hasselberg
Bug: http://curl.haxx.se/mail/lib-2014-03/0134.html