Lifted types & main openssl lib to separate files.

Noticed that typed wrappers for some other libs (e.g., db) would use
the types but not necessarily the functions, so it seems logical to
separate the types.

Also, after I built Racket on my Mac, it failed to find
openssl/main.rkt named as it was — signaled an error that indicated it
was looking in <my git repo>/pkgs/htdp-pkgs/htdp-lib/typed/openssl.rkt
— so I lifted openssl/main.rkt out to openssl.rkt