Fix inconsistencies in the code

This addresses a couple of issues in the code:
- Typos and inconsistencies in comments and function declarations.
- Removal of unreferenced function declarations.
- Removal of unnecessary compile flags.
- A cleanup error in regressplans.sh.

Author: Alexander Lakhin
Discussion: https://postgr.es/m/0c991fdf-2670-1997-c027-772a420c4604@gmail.com

src/backend/executor/README

@@ -186,9 +186,9 @@ Expression Evaluation
 
 To allow for different methods of expression evaluation, and for
 better branch/jump target prediction, expressions are evaluated by
-calling ExprState->evalfunc (via ExprEvalExpr() and friends).
+calling ExprState->evalfunc (via ExecEvalExpr() and friends).
 
-ExprReadyExpr() can choose the method of interpretation by setting
+ExecReadyExpr() can choose the method of interpretation by setting
 evalfunc to an appropriate function.  The default execution function,
 ExecInterpExpr, is implemented in execExprInterp.c; see its header
 comment for details.  Special-case evalfuncs are used for certain

src/backend/executor/execScan.c

@@ -98,8 +98,7 @@ ExecScanFetch(ScanState *node,
  *		ExecScan
  *
  *		Scans the relation using the 'access method' indicated and
- *		returns the next qualifying tuple in the direction specified
- *		in the global variable ExecDirection.
+ *		returns the next qualifying tuple.
  *		The access method returns the next tuple and ExecScan() is
  *		responsible for checking the tuple returned against the qual-clause.
  *

src/backend/executor/execTuples.c

@@ -1148,7 +1148,7 @@ ExecAllocTableSlot(List **tupleTable, TupleDesc desc,
  *		This releases any resources (buffer pins, tupdesc refcounts)
  *		held by the tuple table, and optionally releases the memory
  *		occupied by the tuple table data structure.
- *		It is expected that this routine be called by EndPlan().
+ *		It is expected that this routine be called by ExecEndPlan().
  * --------------------------------
  */
 void

src/backend/executor/nodeProjectSet.c

@@ -196,8 +196,8 @@ ExecProjectSRF(ProjectSetState *node, bool continuing)
 	Assert(hassrf);
 
 	/*
-	 * If all the SRFs returned EndResult, we consider that as no row being
-	 * produced.
+	 * If all the SRFs returned ExprEndResult, we consider that as no row
+	 * being produced.
 	 */
 	if (hasresult)
 	{

src/backend/executor/nodeRecursiveunion.c

@@ -160,7 +160,7 @@ ExecRecursiveUnion(PlanState *pstate)
 }
 
 /* ----------------------------------------------------------------
- *		ExecInitRecursiveUnionScan
+ *		ExecInitRecursiveUnion
  * ----------------------------------------------------------------
  */
 RecursiveUnionState *
@@ -263,7 +263,7 @@ ExecInitRecursiveUnion(RecursiveUnion *node, EState *estate, int eflags)
 }
 
 /* ----------------------------------------------------------------
- *		ExecEndRecursiveUnionScan
+ *		ExecEndRecursiveUnion
  *
  *		frees any storage allocated through C routines.
  * ----------------------------------------------------------------