Re-sync with the RE repository:

• Prevent duplicate send_logmail() call.
• Add build_ec2_ami() to automatically create EC2 AMIs after the build_release() loop finishes.
• Add ftp_stage() to populate /R/ftp-stage within the chroot, called by build_release().
• Remove call to 'remake-memstick.sh' after r283307.
• Ensure BOARDNAME, BUILDDATE, EMBEDDEDBUILD, and SVNREVISION are passed to the make(1) environment in ftp_stage().

Sponsored by: The FreeBSD Foundation