Clean up temp installations after client program tests.

Commit 7d0f493f19607774fdccb1a1ea06fdd96a3d9698 added infrastructure
to perform tests in assorted src/bin/ subdirectories, but forgot to
teach "make clean" to clean up the detritus the tests leave behind.
Fix off-by-one bug in LWLockRegisterTranche().

Original coding failed to enlarge the array as required if
the requested tranche_id was equal to LWLockTranchesAllocated.

In passing, fix poor style of not casting the result of (re)palloc.
Record the proper typmod for an index expression column.

We should use exprTypmod() to extract the typmod of the expression,
instead of just blindly storing -1.  This seems to have been an aboriginal
oversight in commit fc8d970cbcdd6f025475822a4cf01dfda0873226 which
introduced general-expression indexes.  The consequences are only cosmetic
at present, since the index machinery doesn't really look at typmod for
index columns; but still it seems best to describe the column type as
precisely as we can.  Per off-list complaint from Thomas Fanghaenel.