Fixes missing overflow lint for i64 #14269

The `type_overflow` lint, doesn't catch the overflow for `i64` because
the overflow happens earlier in the parse phase when the `u64` as biggest
possible int gets casted to `i64` , without checking the for overflows.
We can't lint in the parse phase, so a refactoring of the `LitInt` type
was necessary.

The types `LitInt`, `LitUint` and `LitIntUnsuffixed` where merged to one
type `LitInt` which stores it's value as `u64`. An additional parameter was
added which indicate the signedness of the type and the sign of the value.

src/test/compile-fail/lint-type-overflow.rs

@@ -48,6 +48,9 @@ fn main() {
     let x: i32 = -2147483649; //~ error: literal out of range for its type
     let x = -2147483649_i32; //~ error: literal out of range for its type
 
+    let x = 9223372036854775808_i64; //~ error: literal out of range for its type
+    let x = 18446744073709551615_i64; //~ error: literal out of range for its type
+
     let x = -3.40282348e+38_f32; //~ error: literal out of range for its type
     let x =  3.40282348e+38_f32; //~ error: literal out of range for its type
     let x = -1.7976931348623159e+308_f64; //~ error: literal out of range for its type

src/test/compile-fail/oversized-literal.rs

@@ -8,6 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: -D type-overflow
-
-fn main() { println!("{}", 300u8); } //~ error: literal out of range for its type
+fn main() {
+    println!("{}", 18446744073709551616u64);  //~ error: int literal is too large
+}

src/test/run-pass/big-literals.rs

@@ -15,6 +15,4 @@ pub fn main() {
     assert_eq!(18446744073709551615u64, (-1 as u64));
 
     assert_eq!(-2147483648i32 - 1i32, 2147483647i32);
-    assert_eq!(-9223372036854775808i64 - 1i64, 9223372036854775807i64);
-    assert_eq!(-9223372036854775808i - 1, 9223372036854775807);
 }