Added ArrayList.initCapcity() as a way to preallocate a block of memory to reduce future allocations.
Added a test "std.ArrayList.initCapacity" that ensures initCapacity adds no elements and increases capacity by at least the requested amount
* Add some documentation for standard library things.
Added a bunch of descriptions for array_list.
Added some usage notes for failing_allocator.
Documented some of mem.Allocator.