diff: add pred_or_func to higher_order_call goals

[Fergus Henderson]

Fix a bug for the case of a higher-order function call in code
with common sub-expression; mercury 0.7 failed this test, reporting
"Software Error: modecheck fails when repeated", due to confusion
between h.o. _function_ call and h.o. _predicate_ call.

compiler/hlds_goal.m:
	Add a new `pred_or_func' field to HLDS higher_order_calls.

compiler/modes.m:
compiler/modecheck_call.m:
compiler/hlds_out.m:
compiler/*.m:
	Add code to handle the new field for higher_order_call goals.

tests/valid/Mmake:
tests/valid/ho_func_call.m:
	Regression test for the above-mentioned bug.


-- 
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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