Add inline const macro test

Author: spastorino

src/test/ui/inline-const/const-expr-macro.rs

@@ -0,0 +1,12 @@
+// run-pass
+
+#![allow(incomplete_features)]
+#![feature(inline_const)]
+macro_rules! do_const_block{
+    ($val:block) => { const $val }
+}
+
+fn main() {
+    let s = do_const_block!({ 22 });
+    assert_eq!(s, 22);
+}