The current source-to-source debugger transformation cannot handle the
predicates introduced by higher-order specialization. There are likely similar
issues with other HLDS->HLDS transformations.
The fix (for now) is to disable most HLDS->HLDS transformations in .ssdebug
grades.
compiler/handle_options.m:
Disable most HLDS->HLDS optimizations when the ss-trace level is
shallow or deep.
Add an XXX comment about a separate issue.
compiler/ssdebug.m:
Add an XXX comment about predicates produced by higher-order
specialization.
tests/WS_FLAGS.ws:
Add a missing include.
tests/valid/Mmakefile:
tests/valid/Mercury.options:
tests/valid/gh89.m:
Add the test case from github issue 89.
