Add base support for invoking custom functions (arguments' evaluating is still not supported)

modules/io/src/main/kotlin/io/smnp/ext/io/function/PrintlnFunction.kt

@@ -8,7 +8,7 @@ import io.smnp.type.model.Value
 
 class PrintlnFunction : Function("println") {
     override fun define(new: FunctionDefinitionTool) {
-        new function vararg(allTypes()) define { _module,  (vararg) ->
+        new function vararg(allTypes()) body { _,  (vararg) ->
             // TODO: Implement equivalent of "toString()" method
             println((vararg.value!! as List<Value>).joinToString("") { it.value!!.toString() })
             Value.void()

modules/lang/src/main/kotlin/io/smnp/ext/lang/function/DebugFunction.kt

@@ -7,7 +7,7 @@ import io.smnp.type.model.Value
 
 class DebugFunction : Function("debug") {
     override fun define(new: FunctionDefinitionTool) {
-        new function simple() define { env, _ ->
+        new function simple() body { env, _ ->
             env.printCallStack()
             Value.void()
         }