* include/wget/wget.h: Convert wget_http_connection_t to forward declaration
* libwget/http.h: Move wget_http_connection_t definition here
* libwget/Makefile.am: Add new file http.h
* libwget/http.c: Include http.h and add accessor functions
* libwget/http_highlevel.c: Include http.h
* src/wget.c: Replace access to wget_http_connection_t with accessor function calls
