http: fix multi part files
Created by: giuseppe
- src/wget.c (download_part): Read temp part for the temporary files. (_get_header): Write part file to a temporary file. (http_get): Keep a temporary fd for the file parts. (struct _body_callback_context): Add 'head' and 'part'.
- src/job.h (struct PART): Add 'tmp_fd'.
- src/job.c (job_create_parts): Initialize tmp_fd.
- autogen.sh (libwget_gnulib_modules): add 'safe-read'
Signed-off-by: Giuseppe Scrivano gscrivan@redhat.com