hashtable documentation

[Hoehle, Joerg-C. <Joe...@t-...>]

Hi,

I read some of impnotes and fixed a few missing specifications (I only read a small part of it).

While doing so, I noticed problems with hashtabl.d:

1. Line 72ff and line 1369 differ in what they document. I believe the former to be obsolete and the latter up to date.

2. in make_hash_table, coerce_function(...); pushSTACK(test); looks like a GC-SAFETY bug to me.

3. I think the hash-table section of impnotes needs more updates than what I did.
 - :value-type and:key-type are not documented
 - maybe other things changed since fasthash, I felt unsure about that.

Regards,
	Jorg Hohle.