Missing warning on some cases of integer literal coercion

[fairywreath]

These properly give warnings:

    int x1 = 0xffffffffffff;
    int x2 = -9223372036854775807;

1.slang(36): warning 30081: implicit conversion from 'uint64_t' to 'int' is not recommended
    int x1 = 0xffffffffffff;
             ^~~~~~~~~~~~~~~
1.slang(38): warning 30081: implicit conversion from 'int64_t' to 'int' is not recommended
    int x2 = -9223372036854775807;
              ^~~~~~~~~~~~~~~~~~~

But these do not(note they are assigned to UINT64_MAX)

    int x3 = 18446744073709551615;
    int x4 = 0xFFFFFFFFFFFFFFFF;

This needs to be investigated and fixed.

[jkwak-work]

It appears that I am getting a little different error message with ToT.

tests/compute/frem.slang(14): warning 30081: implicit conversion from 'int64_t' to 'int' is not recommended
    int x1 = 0xffffffffffff;
             ^~~~~~~~~~~~~~

tests/compute/frem.slang(15): warning 30081: implicit conversion from 'int64_t' to 'int' is not recommended
    int x2 = -9223372036854775807;
              ^~~~~~~~~~~~~~~~~~~

tests/compute/frem.slang(16): warning 39999: integer literal is too large to be represented in a signed integer type, interpreting as unsigned
    int x3 = 18446744073709551615;
             ^~~~~~~~~~~~~~~~~~~~

It sounds all correct.
Only problem I see is that x4 is not printing a warning.