Add Stmt and incorporate meta statements

This helps split up expressions, meta calls (like includes) that can be
expanded into more expressions.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/vm/machine.rs

@@ -1,7 +1,7 @@
 use crate::compile::Compile;
 use crate::object::*;
 use crate::scope::*;
-use crate::syn::ast::SpExpr;
+use crate::syn::ast::SpStmt;
 use crate::vm::{error::*, inst::*};
 use std::cell::RefCell;
 use std::collections::BTreeMap;
@@ -175,10 +175,10 @@ impl Machine {
     // Eval
     // /////////////////////////////////////////////////////////////////////////
 
-    pub fn eval(&mut self, exprs: &Vec<SpExpr>) -> Result<()> {
+    pub fn eval(&mut self, stmts: Vec<SpStmt>) -> Result<()> {
         self.scope_stack.push_scope();
         let mut compile = Compile::new(&mut self.scope_stack, &mut self.quote_table);
-        let code = Rc::new(compile.compile(exprs));
+        let code = Rc::new(compile.compile(stmts));
         let locals = self.scope_stack.pop_scope().unwrap();
         self.call_stack.push(
             QuoteFrame {