If init is passed by value, it won't be copied, but moved.
If the allocator of ($D_PARAM init) matches allocator,
$(D_KEYWORD this) will just take the ownership over init's
storage, otherwise, the storage will be allocated with
allocator. init will be destroyed at the end.
If init is passed by reference, it will be copied.
Initializes this string from another one.
If init is passed by value, it won't be copied, but moved. If the allocator of ($D_PARAM init) matches allocator, $(D_KEYWORD this) will just take the ownership over init's storage, otherwise, the storage will be allocated with allocator. init will be destroyed at the end.
If init is passed by reference, it will be copied.