Merge branch 'ms/http-no-more-failonerror'

Debugging help for http transport.

* ms/http-no-more-failonerror:
  test: test GIT_CURL_VERBOSE=1 shows an error
  remote-curl: unset CURLOPT_FAILONERROR
  remote-curl: define struct for CURLOPT_WRITEFUNCTION
  http: enable keep_error for HTTP requests
  http: support file handles for HTTP_KEEP_ERROR

diff --cc http.c
Simple merge

diff --cc remote-curl.c
Simple merge