Remove wildcard re-exports of context types

Wildcards make it hard to grep for where stuff comes from, explicit
imports and re-exports are ... more explicit.

Import and re-export explicitly instead of by using wildcards.

src/context.rs

@@ -5,7 +5,7 @@ use core::mem::ManuallyDrop;
 use core::ptr::NonNull;
 
 #[cfg(feature = "alloc")]
-pub use self::alloc_only::*;
+pub use self::alloc_only::{All, SignOnly, VerifyOnly};
 use crate::ffi::types::{c_uint, c_void, AlignedType};
 use crate::ffi::{self, CPtr};
 use crate::{Error, Secp256k1};

src/lib.rs

@@ -174,8 +174,8 @@ use core::marker::PhantomData;
 use core::ptr::NonNull;
 use core::{fmt, mem, str};
 
-#[cfg(feature = "global-context")]
-pub use context::global::SECP256K1;
+#[cfg(all(feature = "global-context", feature = "std"))]
+pub use context::global::{self, SECP256K1};
 #[cfg(feature = "hashes")]
 use hashes::Hash;
 #[cfg(feature = "rand")]
@@ -184,7 +184,12 @@ pub use secp256k1_sys as ffi;
 #[cfg(feature = "serde")]
 pub use serde;
 
-pub use crate::context::*;
+#[cfg(feature = "alloc")]
+pub use crate::context::{All, SignOnly, VerifyOnly};
+pub use crate::context::{
+    AllPreallocated, Context, PreallocatedContext, SignOnlyPreallocated, Signing, Verification,
+    VerifyOnlyPreallocated,
+};
 use crate::ffi::types::AlignedType;
 use crate::ffi::CPtr;
 pub use crate::key::{PublicKey, SecretKey, *};