* .gitignore: New entry examples/http_multi_get
* Makefile.am: Move subdir 'examples' before 'src'
* examples/Makefile.am: Add http_multi_get
* examples/http_get2.c (main): Adapt code to API changes
* examples/http_multi_get.c: New example to show async/parallel
requests
* examples/websequencediagram.c (main): Adapt code to API changes
* include/libwget.h.in: New functions wget_http_request_set_header_cb,
wget_http_request_set_body_cb, wget_http_request_set_int.
Changed params of wget_http_get_response.
Removed wget_http_get_response_func, wget_http_get_response_stream,
wget_http_get_response_fd.
Changed params of wget_http_get_response_cb.
Add members pending_requests, received_http2_responses,
pending_http2_requests to wget_http_connection_t.
Add member req to wget_http_response_t.
Add members header_callback, body_callback, header_user_data,
body_user_data, response_keepheader to wget_http_request_t.
New function types wget_http_header_callback_t and
wget_http_body_callback_t.
* libwget/http.c: Implementation of the changes in include/libwget.h.in.
* libwget/http_highlevel.c: Adapt code to API changes
* libwget/ssl_gnutls.c: Fixed defaults for SNI, OCSP and
ALPN.
Adapt code to API changes.
* src/options.c: Reflect changes in libwget/ssl_gnutls.c
* src/wget.c: Adapt code to API changes
Cookies: Add new function wget_cookie_set_keep_session_cookies()
and adjust wget_cookie_db_load() and wget_cookie_db_save().
Use wget_update_file() for loading and saving.
