For statement type inference bug with HashTable

[hopscc]

Erroneous compilation error

htbl=HashTable()
htbl['a'] ='value1'
...
for de in htbl
  # de to DictionaryEntry  # works if cast explicitly
  print de.key, de.value

gives error

Cannot find a definition for "key" in "de" whose type is "Object?

Should be able to infer type of de as DictionaryEntry
See discussion and fixup area of attack in
 Type inference bug with hashTable and for

Not seen as major since Hashtable not used frequently...

[hopscc]

Fix for this bug, testfile and relnotes add.
Since this disallowed multiarg assignment in a for-statement from a hashtable,
that test in multiarg-forDict tests is also updated...

[Chuck]

Applied in changeset:1710