Upstream: fix NGX_COMPAT build without NGX_HTTP_SSL after 454ad0e.

Please update the synopsis to follow preceding commit logs.

I like to explicitly describe the combination of configure parameters that led to build failure,
to make a better visibility for those who might step on this.

This makes it to:

Upstream: fixed --with-compat build without SSL, broken by 454ad0e.

Or:

Upstream: fixed --with-compat build without SSL.

Broken by 454ad0e (not yet released).

I don't like the place where typedef is inserted,
this will further worsen typedef's prefix based grouping.

ngx_ssl_t and ngx_ssl_connection_t were originally located next to each other,
reflecting their struct declarations in ngx_event_openssl.h.

I'd try to place the new typedef somewhere next to them.