Library restructure (#104)

* Move wasmer-runtime to wasmer-runtime-core

* Add the runtime library

* Fix issue with macros using wasmer_runtime, fmt

* Make default compiler dependency optional

* Add instantiate and validate functions

lib/runtime-core/src/lib.rs

@@ -0,0 +1,70 @@
+#[cfg(test)]
+#[macro_use]
+extern crate field_offset;
+
+#[macro_use]
+mod macros;
+#[doc(hidden)]
+pub mod backend;
+mod backing;
+pub mod error;
+pub mod export;
+pub mod import;
+pub mod instance;
+pub mod memory;
+pub mod module;
+mod sig_registry;
+pub mod structures;
+mod sys;
+pub mod table;
+pub mod types;
+pub mod vm;
+#[doc(hidden)]
+pub mod vmcalls;
+
+use self::error::CompileResult;
+#[doc(inline)]
+pub use self::error::Result;
+#[doc(inline)]
+pub use self::instance::Instance;
+#[doc(inline)]
+pub use self::module::Module;
+use std::rc::Rc;
+
+pub mod prelude {
+    pub use crate::import::{ImportObject, Namespace};
+    pub use crate::types::{
+        FuncIndex, GlobalIndex, ImportedFuncIndex, ImportedGlobalIndex, ImportedMemoryIndex,
+        ImportedTableIndex, LocalFuncIndex, LocalGlobalIndex, LocalMemoryIndex, LocalTableIndex,
+        MemoryIndex, TableIndex, Type, Value,
+    };
+    pub use crate::vm;
+    pub use crate::{export_func, imports};
+}
+
+/// Compile a webassembly module using the provided compiler.
+pub fn compile_with(
+    wasm: &[u8],
+    compiler: &dyn backend::Compiler,
+) -> CompileResult<module::Module> {
+    let token = backend::Token::generate();
+    compiler
+        .compile(wasm, token)
+        .map(|inner| module::Module::new(Rc::new(inner)))
+}
+
+/// This function performs validation as defined by the
+/// WebAssembly specification and returns true if validation
+/// succeeded, false if validation failed.
+pub fn validate(wasm: &[u8]) -> bool {
+    use wasmparser::WasmDecoder;
+    let mut parser = wasmparser::ValidatingParser::new(wasm, None);
+    loop {
+        let state = parser.read();
+        match *state {
+            wasmparser::ParserState::EndWasm => break true,
+            wasmparser::ParserState::Error(_) => break false,
+            _ => {}
+        }
+    }
+}