Make nudb work in 32-bit architectures

[vinniefalco]

Every line of code needs to be inspected and verified for 32/64 bit correctness.

[vinniefalco]

For example dat_file_header lists appnum as std::uint64_t which is correct, but verify_info lists appnum as std::size_t, which is incorrect when sizeof(std::size_t) != 8.

[vinniefalco]

The integer warnings should be re-enabled on the CMakeLists.txt and Jamfile and then every line inspected