url: a short host name + port is not a scheme

The function identifying a leading "scheme" part of the URL considered a
few letters ending with a colon to be a scheme, making something like
"short:80" to become an unknown scheme instead of a short host name and
a port number.

Extended test 1560 to verify.

Also fixed test203 to use file_pwd to make it get the correct path on
windows. Removed test 2070 since it was a duplicate of 203.

Assisted-by: Marcel Raad
Reported-by: Hagai Auro
Fixes #3220
Fixes #3233
Closes #3223
Closes #3235

lib/urlapi.c

@@ -238,7 +238,7 @@ bool Curl_is_absolute_url(const char *url, char *buf, size_t buflen)
 #endif
   for(i = 0; i < buflen && url[i]; ++i) {
     char s = url[i];
-    if(s == ':') {
+    if((s == ':') && (url[i + 1] == '/')) {
       if(buf)
         buf[i] = 0;
       return TRUE;