[m-rev.] for post-commit review: fix mantis bug #522

[Zoltan Somogyi]

As it happens, I could debug bug 552 without an mmc --make
equivalent of lmc, because as the attached HLDS dump shows,
the only nontrivial code between the definition and the use of
Text_287, the variable for which the map.lookup failed, was
a negation. The attached main diff fixes this bug, and the extra
diff fixes minor issues I found while looking for the bug.
For review by anyone.

By the way, I tried but failed to create a test case for this bug.
The reason is that the heart of the bug here is the code
`not (true, false)', and I didn't have the patience to try to
find a way to get this code to the code generator *without*
having the pre-codegen simplification pass delete the whole goal.

Zoltan.
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