Added tests 633 through 637 to test the new file range support for SFTP.

All but the first test cause an infinite loop or other failure and so
are added to DISABLED.

tests/data/test635

@@ -0,0 +1,42 @@
+<testcase>
+<info>
+<keywords>
+SFTP
+Range
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data>
+ssh test
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+sftp
+</server>
+ <name>
+SFTP retrieval with byte range relative to end of file
+ </name>
+ <command>
+--key curl_client_key --pubkey curl_client_key.pub -u %USER: sftp://%HOSTIP:%SSHPORT%PWD/log/file635.txt -r -9
+</command>
+<file name="log/file635.txt">
+Test data
+for ssh test
+</file>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<valgrind>
+disable
+</valgrind>
+</verify>
+</testcase>