Turn `size_t` into an alias for `tpie::stream_size_type`

[SSoelvsten]

The tpie::stream_size_type is designed specifically to ensure large enough numbers are supported on a system, e.g. on some systems std::size_t is a 32-bit integer whereas tpie::stream_size_type always is (at least?) 64-bits.

[SSoelvsten]

Also, we should use std::size_t from <stddef.h> if anything rather than size_t from <stdint.h>. Based on the machine type in question (does it have 64-bit support or not?) we can define the adiar::size_t.