move generated code into its own file.

simplify expr by merging all simple eval functions
into a single eval interface{}.

R=austin
DELTA=1597  (730 added, 780 deleted, 87 changed)
OCL=34182
CL=34198

usr/austin/eval/Makefile

@@ -10,6 +10,7 @@ GOFILES=\
 	bridge.go\
 	compiler.go\
 	expr.go\
+	expr1.go\
 	func.go\
 	scope.go\
 	stmt.go\

usr/austin/eval/stmt.go

@@ -458,7 +458,7 @@ func (a *stmtCompiler) compileIncDecStmt(s *ast.IncDecStmt) {
 
 	one := l.newExpr(IdealIntType, "constant");
 	one.pos = s.Pos();
-	one.evalIdealInt = func() *bignum.Integer { return bignum.Int(1) };
+	one.eval = func() *bignum.Integer { return bignum.Int(1) };
 
 	binop := l.compileBinaryExpr(op, l, one);
 	if binop == nil {