Suggest module, Working class functions misuse ObjStack buffer.

In the suggest module, Wording class we use the  ObjStack buffer
member to accumulate a suggestion (aka nearmiss). See functions
form_word, try_word_n, and try_word_c. We append to buffer more
then once. We assume that the size of the buffer is the end of
the last memory location allocated minus the start of the first
memory allocation. That will fail when one of the appends results
in a reallocation due to exceeding the memory available in the
current block.

I haven't desided what to do. I may suggest a patch that uses the
String class to accumulate the suggestion, since ObjStack doesn't
seem to be a good choice for the task at hand.

Any suggestion are wellcome.
Gary