(chore) consistent setter behavior

- Resolves wren-lang#54

Author: joshgoebel

src/module/io.c

@@ -522,6 +522,7 @@ void stdinIsRawSet(WrenVM* vm)
     // Can't set raw mode when not talking to a TTY.
     // TODO: Make this a runtime error?
   }
+  wrenSetSlotBool(vm, 0, isStdinRaw);
 }
 
 void stdinIsTerminal(WrenVM* vm)

test/io/stdin/is_raw.wren

@@ -26,3 +26,6 @@ for (i in 1..4) {
 // TODO: This doesn't actually detect a visible difference between raw and
 // non-raw mode. Maybe add support to the test runner for writing non-printing
 // characters to stdin?
+
+System.print(Stdin.isRaw=false) // expect: false
+System.print(Stdin.isRaw=true) // expect: true