Make hash-table support numbers as keys

[nagy]

This allows numbers to be used as hash-table keys, since they are crudely converted to strings.

Closes #424

[vlad-km]

@nagy, thanks. Sorry, very busy lately. I'll take a look at the code this weekend.

[davazp]

I think a requirement for this change is that (gethash 1 ht) should be different from (gethash "1" ht), of even for JS objects.

For #'eq hash tables, we could just probably use a Map.

But that doen't solve the problem for #'eql hash-tables.

[nagy]

that (gethash 1 ht) should be different from (gethash "1" ht)

You are right, I will think of a different approach.

[hemml]

May be we can store keys as strings like "TYPE:VALUE", for example "1" will be converted to "string:1" and 1 will be "number:1", etc.

[nagy]

To my surprise, that distinction between numbers and strings is already happening correctly. I have split the commit into two and added some more test and wrote some reasoning into the commit message.

Please check if it is fine now.

[davazp]

Awesome! Thanks!