[scponly] Work around for --with-sftp-server option

[Paul Hyder]

One option for the problems seen recently with the --with-sftp-server flag
to configure is to temporarily add the correct location for sftp-server to
the end of the shell's PATH and to not use the --with-sftp-server option.
[The problem is seen when --with-sftp server is used with --enable-scp-compat]

This should address the cases where sftp-server is not found in any default
location.  It might not help if you want to specify an alternate sftp-server
but careful selection of PATH order should also work there.

Please note that the addition of the path for the sftp-server binary should
NOT be as the first or second PATH entry.  (Autoconf generates interesting
configure code.  Let me know if you want to know more.)
	Paul Hyder
	NOAA Earth System Research Laboratory, Global Systems Division
	Boulder, CO