v5, 5 partsnew roll of proxy improvements

The changes from v4 are:
- In patch 1/5, read proxy env var accordingly to the protocol used in
the destination url, so e.g. if url is a https one, we will only read 
https_proxy env var. We also read no_proxy env var so to ignore 
aforementioned proxy env var if no_proxy contains an asterisk ('*') or 
contains the host used in url destination. To make those changes
possible we needed to pass the destination url as a parameter to 
get_active_slot() and get_curl_handle() functions, so that change is
also included in the patch.

- In patch 2/5, added Junio review fixes.

Regards,

Nelson Benitez Leon (5):
  http: try http_proxy env var when http.proxy config option is not set
  http: handle proxy proactive authentication
  http: handle proxy authentication failure (error 407)
  http: Avoid limit of retrying request only twice
  http: rename HTTP_REAUTH to HTTP_RETRY

 http-push.c   |   24 ++++++++--------
 http-walker.c |    2 +-
 http.c        |   84 ++++++++++++++++++++++++++++++++++++++++++++++++---------
 http.h        |    4 +-
 remote-curl.c |    4 +-
 5 files changed, 88 insertions(+), 30 deletions(-)