Merge branch 'tz/send-email-negatable-options' into maint-2.43

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

diff --cc Documentation/CodingGuidelines
Simple merge

diff --cc git-send-email.perl
Simple merge

diff --cc git-svn.perl
Simple merge