Unused parameters & co in code

Hi all,

I just got a run with CFLAGS with the following options:
-Wunused-function -Wunused-variable -Wunused-const-variable
-Wno-unused-result -Wunused-parameter -Wunused-macros

And while this generates a lot of noise for callbacks and depending on
the environment used, this is also pointing to things which could be
simplified:

Unused arguments in functions:
heap_getsysattr() => tupleDesc
brin_start_evacuating_page() => idxRel
UpdateIndexRelation() => parentIndexOid
SerializeReindexState() => maxsize
ginRedoInsertEntry() => isLeaf
ginReadTuple() => ginstate, attnum
startScanKey() => ginstate
resolve_unique_index_expr() => heapRel
gistGetNodeBuffer() => giststate
heap_tuple_needs_freeze() => buf
log_heap_visible() => rnode
transformSQLValueFunction() => pstate
HeapTupleSatisfiesSelf() => snapshot, buffer
HeapTupleSatisfiesAny() (Style enforced by HeapTupleSatisfiesVisibility)
_hash_get_newbucket_from_oldbucket => rel
RelationPutHeapTuple => relation
checkNameSpaceConflicts => pstate
toast_delete_datum => rel
visibilitymap_clear => rel
_bt_relbuf => rel (Quite some cleanup here for the btree code)
ReindexPartitionedIndex => parentIdx
assignOperTypes => typeinfo
storeProcedures => amoid
dropOperators => amoid
dropProcedures => amoid
ATExecColumnDefault => lockmode
rename_constraint_internal => recursing
ATExecDropIdentity => recursing
ATPrepSetStatistics => colNum, newValue, lockmode
ATExecAlterColumnGenericOptions => lockmode
ATPostAlterTypeParse => lockmode
ATExecEnableDisableRule => lockmode
sendAuthRequest => port (Quite some simplification)
get_qual_from_partbound => rel
alloc_edge_table, free_edge_table, gimme_edge, remove_gene => root
set_tablefunc_pathlist => rte
cost_bitmap_and_node
cost_gather_merge
cost_gather
eclass_useful_for_merging => root
initial_cost_hashjoin
clear_external_function_hash => filehandle (could be extended)
pg_SASL_init => payloadlen
reached_end_position => timeline, segment_finished
syncTargetDirectory => argv0
parseAclItem => name
describeAggregates => verbose
blackholeNoticeProcessor => arg

There are also some unused constants and macros:
PREFER in regcomp.c
STATHDRSIZE in tsvector_op.c
NAMESPACE_SQLXML in xml.c (here for documentation)
messageEquals in parallel.c

For some of these functions, the format is determined by the context,
take HeapTupleSatisfiesSelf or some planner routines. For others, it
usually comes from some code deleted which did not actually correct
the related function. Anyway, simplifying all that means usually a
back-patch pain. However, in some cases, like for example _bt_relbuf,
ReindexPartitionedIndex or sendAuthRequest it can simplify the code as
there is no need to move some extra arguments around from an upper
layer. Fixing all of these makes little sense, still it seems to me
that the cases where we can get extra simplifications for other code
paths calling the functions makes sense and that we should fix them.

Thoughts?
--
Michael