Merge branch 'tz/send-email-negatable-options'

Newer versions of Getopt::Long started giving warnings against our (ab)use of it in "git send-email". Bump the minimum version requirement for Perl to 5.8.1 (from September 2002) to allow simplifying our implementation. * tz/send-email-negatable-options: send-email: avoid duplicate specification warnings perl: bump the required Perl version to 5.8.1 from 5.8.0