Test for unnecessary_cast of hex int literal.

Author: mlegner

tests/ui/unnecessary_cast_fixable.fixed

@@ -14,4 +14,5 @@ fn main() {
     &v as &[i32];
     1.0 as f64;
     1 as u64;
+    0x42 as f32;
 }

tests/ui/unnecessary_cast_fixable.rs

@@ -14,4 +14,5 @@ fn main() {
     &v as &[i32];
     1.0 as f64;
     1 as u64;
+    0x42 as f32;
 }