test: Add tests for #1802

Author: brson

src/test/compile-fail/issue-1802-1.rs

@@ -0,0 +1,4 @@
+// error-pattern:no valid digits found for number
+fn main() {
+    log(error, 0b42);
+}

src/test/compile-fail/issue-1802-2.rs

@@ -0,0 +1,4 @@
+// error-pattern:no valid digits found for number
+fn main() {
+    log(error, 0bu);
+}