Literals are Lvalues

Implement size_t literal_addr_delta(void): take the address of the string literal "ca" twice (two separate &"ca"[0] expressions), return the byte distance between them as a size_t (0 if equal). Then implement int literal_is_lvalue(void) returning 1 unconditionally — because taking that address compiled at all, proving literals are lvalues (modifying them would be UB, not a compile error).