Retire a few backwards compatibility macros.

As of commits dd04e958c8 and 1833f1a1c3, tuplestore_donestoring(),
SPI_push(), SPI_pop(), SPI_push_conditional(),
SPI_pop_conditional(), and SPI_restore_connection() are no-op
macros provided for backwards compatibility.  This commit removes
these macros, so any uses in third-party code will need to be
removed, too.  Since these macros have been no-ops for a while,
such adjustments won't produce any behavior changes for all
currently-supported versions of PostgreSQL.

Author: Bharath Rupireddy
Discussion: https://postgr.es/m/CALj2ACVeO58JM5tK2Qa8QC-%3DkC8sdkJOTd4BFU%3DK8zs4gGYpjQ%40mail.gmail.com

src/include/executor/spi.h

@@ -100,13 +100,6 @@ typedef struct _SPI_plan *SPIPlanPtr;
 
 #define SPI_OPT_NONATOMIC		(1 << 0)
 
-/* These used to be functions, now just no-ops for backwards compatibility */
-#define SPI_push()	((void) 0)
-#define SPI_pop()	((void) 0)
-#define SPI_push_conditional()	false
-#define SPI_pop_conditional(pushed) ((void) 0)
-#define SPI_restore_connection()	((void) 0)
-
 extern PGDLLIMPORT uint64 SPI_processed;
 extern PGDLLIMPORT SPITupleTable *SPI_tuptable;
 extern PGDLLIMPORT int SPI_result;

src/include/utils/tuplestore.h

@@ -56,9 +56,6 @@ extern void tuplestore_puttuple(Tuplestorestate *state, HeapTuple tuple);
 extern void tuplestore_putvalues(Tuplestorestate *state, TupleDesc tdesc,
 								 const Datum *values, const bool *isnull);
 
-/* Backwards compatibility macro */
-#define tuplestore_donestoring(state)	((void) 0)
-
 extern int	tuplestore_alloc_read_pointer(Tuplestorestate *state, int eflags);
 
 extern void tuplestore_select_read_pointer(Tuplestorestate *state, int ptr);