Add trailing commas to enum definitions

Since C99, there can be a trailing comma after the last value in an
enum definition.  A lot of new code has been introducing this style on
the fly.  Some new patches are now taking an inconsistent approach to
this.  Some add the last comma on the fly if they add a new last
value, some are trying to preserve the existing style in each place,
some are even dropping the last comma if there was one.  We could
nudge this all in a consistent direction if we just add the trailing
commas everywhere once.

I omitted a few places where there was a fixed "last" value that will
always stay last.  I also skipped the header files of libpq and ecpg,
in case people want to use those with older compilers.  There were
also a small number of cases where the enum type wasn't used anywhere
(but the enum values were), which ended up confusing pgindent a bit,
so I left those alone.

Discussion: https://www.postgresql.org/message-id/flat/386f8c45-c8ac-4681-8add-e3b0852c1620%40eisentraut.org

src/backend/optimizer/path/allpaths.c

@@ -74,7 +74,7 @@ typedef enum pushdown_safe_type
 {
 	PUSHDOWN_UNSAFE,			/* unsafe to push qual into subquery */
 	PUSHDOWN_SAFE,				/* safe to push qual into subquery */
-	PUSHDOWN_WINDOWCLAUSE_RUNCOND	/* unsafe, but may work as WindowClause
+	PUSHDOWN_WINDOWCLAUSE_RUNCOND,	/* unsafe, but may work as WindowClause
 									 * run condition */
 } pushdown_safe_type;
 

src/backend/optimizer/path/indxpath.c

@@ -45,7 +45,7 @@ typedef enum
 {
 	ST_INDEXSCAN,				/* must support amgettuple */
 	ST_BITMAPSCAN,				/* must support amgetbitmap */
-	ST_ANYSCAN					/* either is okay */
+	ST_ANYSCAN,					/* either is okay */
 } ScanTypeControl;
 
 /* Data structure for collecting qual clauses that match an index */

src/backend/optimizer/plan/setrefs.c

@@ -35,7 +35,7 @@ typedef enum
 {
 	NRM_EQUAL,					/* expect exact match of nullingrels */
 	NRM_SUBSET,					/* actual Var may have a subset of input */
-	NRM_SUPERSET				/* actual Var may have a superset of input */
+	NRM_SUPERSET,				/* actual Var may have a superset of input */
 } NullingRelsMatch;
 
 typedef struct

src/backend/optimizer/util/pathnode.c

@@ -40,7 +40,7 @@ typedef enum
 	COSTS_EQUAL,				/* path costs are fuzzily equal */
 	COSTS_BETTER1,				/* first path is cheaper than second */
 	COSTS_BETTER2,				/* second path is cheaper than first */
-	COSTS_DIFFERENT				/* neither path dominates the other on cost */
+	COSTS_DIFFERENT,			/* neither path dominates the other on cost */
 } PathCostComparison;
 
 /*

src/backend/optimizer/util/predtest.c

@@ -51,7 +51,7 @@ typedef enum
 {
 	CLASS_ATOM,					/* expression that's not AND or OR */
 	CLASS_AND,					/* expression with AND semantics */
-	CLASS_OR					/* expression with OR semantics */
+	CLASS_OR,					/* expression with OR semantics */
 } PredClass;
 
 typedef struct PredIterInfoData *PredIterInfo;