Add function to create new hashtables with a default size
In other some standard libraries (Java, OCaml), hash tables can be created with a use-supplied size. This avoids rehashing for users who know they will be inserting a lot of data.
Data.HashTable does not expose a function to do this. This proposal changes that.
For a dictionary of 5 million strings, this patch saves me about 33% of the total execution time. For 10 million strings, this patch saves me 50% of the total execution time.