Function std.experimental.allocator.building_blocks.bitmapped_block.BitmappedBlock.allocate
Allocates s bytes of memory and returns it, or null if memory
        could not be allocated.
						
				void[] allocate
				(
				
				  const size_t s
				
				) pure nothrow @nogc @trusted;
						
					
				The following information might be of help with choosing the appropriate
        block size. Actual allocation occurs in sizes multiple of the block size.
        Allocating one block is the fastest because only one 0 bit needs to be
        found in the metadata. Allocating 2 through 64 blocks is the next cheapest
        because it affects a maximum of two ulong in the metadata.
        Allocations greater than 64 blocks require a multiword search through the
        metadata.
        If instantiated with No, it performs a search for the first zero
        bit in the bitmap and sets it.