Fix some deprecated patterns when using BoringSSL

[davidben]

The RSA and DSA changes will be needed to avoid build breakage soon. The others are mostly tidying up. There's another place around BIO that we'd ideally also switch over, but that depends on resolving the __fixed_rust mess first.

This addresses a symptom of #1944, but not the root cause.

(@maurer FYI. Android will need to pick this patch up to avoid causing another problem with BoringSSL updates.)

[davidben]

CI failures are odd. They are with BoringSSL, but I'm also confused how they could be caused by this PR:

error: ambiguous glob re-exports
  --> openssl-sys/src/lib.rs:17:9
   |
17 | pub use libc::*;
   |         ^^^^^^^ the name `FILE` in the type namespace is first re-exported here
...
36 | pub use boringssl::*;
   |         ------------ but the name `FILE` in the type namespace is also re-exported here
   |
   = note: `-D ambiguous-glob-reexports` implied by `-D warnings`

error: ambiguous glob re-exports
  --> openssl-sys/src/lib.rs:17:9
   |
17 | pub use libc::*;
   |         ^^^^^^^ the name `timeval` in the type namespace is first re-exported here
...
36 | pub use boringssl::*;
   |         ------------ but the name `timeval` in the type namespace is also re-exported here

error: ambiguous glob re-exports
  --> openssl-sys/src/lib.rs:17:9
   |
17 | pub use libc::*;
   |         ^^^^^^^ the name `tm` in the type namespace is first re-exported here
...
36 | pub use boringssl::*;
   |         ------------ but the name `tm` in the type namespace is also re-exported here

error: ambiguous glob re-exports
  --> openssl-sys/src/lib.rs:17:9
   |
17 | pub use libc::*;
   |         ^^^^^^^ the name `time_t` in the type namespace is first re-exported here
...
36 | pub use boringssl::*;
   |         ------------ but the name `time_t` in the type namespace is also re-exported here

Is there perhaps an issue with bindgen over-binding things?

[davidben]

I see a similar failure in #1946, so guessing this is not related to this PR and rather the CI broke.