Enable SIMD instructions from the command line (#232)

This change adds an `--enable-simd` flag to the binaries in this project. This allows the ISA `enable_simd` flag to be set and to configure the validation configuration used by wasmparser to allow SIMD instructions.

wasmtime-wast/src/wast.rs

@@ -4,7 +4,7 @@ use std::path::Path;
 use std::{fmt, fs, io, str};
 use wabt::script::{Action, Command, CommandKind, ModuleBinary, ScriptParser, Value};
 use wasmtime_jit::{
-    ActionError, ActionOutcome, Compiler, Context, InstanceHandle, InstantiationError,
+    ActionError, ActionOutcome, Compiler, Context, Features, InstanceHandle, InstantiationError,
     RuntimeValue, UnknownInstance,
 };
 
@@ -85,6 +85,14 @@ impl WastContext {
         }
     }
 
+    /// Construct a new instance with the given features using the current `Context`
+    pub fn with_features(self, features: Features) -> Self {
+        Self {
+            context: self.context.with_features(features),
+            ..self
+        }
+    }
+
     fn get_instance(
         &mut self,
         instance_name: Option<&str>,