Move the wasmtime crate directories form lib/* to wasmtime-*.

This follows a similar change to Cranelift made here:

https://github.com/CraneStation/cranelift/pull/660

wasmtime-runtime/src/lib.rs

@@ -0,0 +1,62 @@
+//! Runtime library support for Wasmtime.
+
+#![deny(missing_docs, trivial_numeric_casts, unused_extern_crates)]
+#![warn(unused_import_braces)]
+#![cfg_attr(feature = "std", deny(unstable_features))]
+#![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
+#![cfg_attr(
+    feature = "cargo-clippy",
+    allow(clippy::new_without_default, clippy::new_without_default_derive)
+)]
+#![cfg_attr(
+    feature = "cargo-clippy",
+    warn(
+        clippy::float_arithmetic,
+        clippy::mut_mut,
+        clippy::nonminimal_bool,
+        clippy::option_map_unwrap_or,
+        clippy::option_map_unwrap_or_else,
+        clippy::print_stdout,
+        clippy::unicode_not_nfc,
+        clippy::use_self
+    )
+)]
+
+#[macro_use]
+extern crate lazy_static;
+#[macro_use]
+extern crate memoffset;
+#[macro_use]
+extern crate failure_derive;
+#[cfg(target_os = "windows")]
+extern crate winapi;
+
+mod export;
+mod imports;
+mod instance;
+mod jit_int;
+mod memory;
+mod mmap;
+mod sig_registry;
+mod signalhandlers;
+mod table;
+mod traphandlers;
+mod vmcontext;
+
+pub mod libcalls;
+
+pub use crate::export::Export;
+pub use crate::imports::Imports;
+pub use crate::instance::{InstanceHandle, InstantiationError, LinkError};
+pub use crate::jit_int::GdbJitImageRegistration;
+pub use crate::mmap::Mmap;
+pub use crate::sig_registry::SignatureRegistry;
+pub use crate::signalhandlers::{wasmtime_init_eager, wasmtime_init_finish};
+pub use crate::traphandlers::{wasmtime_call, wasmtime_call_trampoline};
+pub use crate::vmcontext::{
+    VMContext, VMFunctionBody, VMFunctionImport, VMGlobalDefinition, VMGlobalImport,
+    VMMemoryDefinition, VMMemoryImport, VMSharedSignatureIndex, VMTableDefinition, VMTableImport,
+};
+
+/// Version number of this crate.
+pub const VERSION: &str = env!("CARGO_PKG_VERSION");