pgsql: Clean up a few parallelism-related things that pgindent wants to

Clean up a few parallelism-related things that pgindent wants to mangle.

In nodeFuncs.c, pgindent wants to introduce spurious indentation into
the definitions of planstate_tree_walker and planstate_walk_subplans.
Fix that by spreading the definition out across several lines, similar
to what is already done for other walker functions in that file.

In execParallel.c, in the definition of SharedExecutorInstrumentation,
pgindent wants to insert more whitespace between the type name and the
member name. That causes it to mangle comments later on the line. Fix
by moving the comments out of line. Now that we have a bit more room,
add some more details that may be useful to the next person reading
this code.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/8126eaee2fed7cbc4e9fd6ba8713977ccacd77fe

Modified Files
--------------
src/backend/executor/execParallel.c | 27 +++++++++++++++++++++------
src/backend/nodes/.nodeFuncs.c.swp | Bin 0 -> 122880 bytes
src/backend/nodes/nodeFuncs.c | 8 ++++++--
3 files changed, 27 insertions(+), 8 deletions(-)