Windows PSCP now links against winsftp.c, and scp.c is now a

platform-independent source file. Haven't yet added the extra
abstraction routines to uxsftp.c to create a Unix PSCP port, but it
shouldn't take long.
Also in this checkin, a change of semantics in platform_default_s():
now strings returned from it are expected to be dynamically allocated.

[originally from svn r3420]

settings.c

@@ -29,6 +29,7 @@ static void gpps(void *handle, const char *name, const char *def,
 	pdef = platform_default_s(name);
 	if (pdef) {
 	    strncpy(val, pdef, len);
+	    sfree(pdef);
 	} else {
 	    strncpy(val, def, len);
 	}