[progressmeter.c] allow WARNINGS=yes; ok djm@
[scp.c sftp.1 sftp.c sftp-client.c sftp-int.c progressmeter.c] [progressmeter.h] sftp progress meter support. original diffs by Nils Nordman <nino at nforced dot com> via markus@, merged to -current by me, djm@ ok.