Change __lsan::kMaxAllowedMallocSize literal types to unsigned long long

It is required for the [Leak Sanitizer port to Windows](https://reviews.llvm.org/D115103).
The currently used `unsigned long` type is 64 bits wide on UNIX like systems but only 32 bits wide on Windows.
Because of that, the literal `8UL << 30` causes an integer overflow on Windows.
By changing the type of the literals to `unsigned long long`, we have consistent behavior and no overflows on all Platforms.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D115186