diff: term_errors.m bug fixes

[Fergus Henderson]

Estimated hours taken: 0.5

compiler/term_errors.m:
	Fix some bugs:
	- when printing out the mode number, it needs
	  to take it mod 10000 to strip off the "priority".
	- In some cases, termination analysis infers that a procedure
	  can loop, but the list of reasons why is empty.
	  This should never happen, and so term_errors.m was calling
	  error/1 in this situation, but in practice it does happen,
	  so I've changed term_errors.m to print out an error message
	  with "for unknown reason(s)" in that case.
	  We still ought to fix the problem, but this change at least
	  makes it easier to track down, since the error message says
	  which procedure the problem is occuring for.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>   |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
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