Display libcurl error code/message

[fabricereix]

Hurl should report exactly the same error message than curl when the error has been generated by libcurl.
This will make debugging/searching error easier,

For example:

curl: (6) Could not resolve host: unknown

$ echo GET http://unknown | hurl
error: Http Connection
  --> -:1:5
   |
 1 | GET http://unknown
   |     ^^^^^^^^^^^^^^ (6) Could not resolve host: unknown
   |

[lepapareil]

Displaying lib name causing the error would perhaps be useful for debugging, for example:

curl: (6) Could not resolve host: unknown

$ echo GET http://unknown | hurl
error: Http Connection
  --> -:1:5
   |
 1 | GET http://unknown
   |     ^^^^^^^^^^^^^^ libcurl: (6) Could not resolve host: unknown
   |