chooseAtRuntime is a compile-time constant of type size_t that several
parameterized structures in this module recognize to mean deferral to runtime of
the exact value. For example, BitmappedBlock!(Allocator, 4096) (described in
detail below) defines a block allocator with block size of 4096 bytes, whereas
BitmappedBlock!(Allocator, chooseAtRuntime) defines a block allocator that has a
field storing the block size, initialized by the user.
chooseAtRuntime is a compile-time constant of type size_t that several parameterized structures in this module recognize to mean deferral to runtime of the exact value. For example, BitmappedBlock!(Allocator, 4096) (described in detail below) defines a block allocator with block size of 4096 bytes, whereas BitmappedBlock!(Allocator, chooseAtRuntime) defines a block allocator that has a field storing the block size, initialized by the user.