Add const to read only TableInfo pointers in pg_dump

Functions that dump table data receive their parameters through const
void * but were casting away const.  Add const qualifiers to functions
that only read the table information.

Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://postgr.es/m/aUQHy/MmWq7c97wK%40ip-10-97-1-34.eu-west-3.compute.internal

src/bin/pg_dump/pg_dump.c

@@ -2380,8 +2380,8 @@ selectDumpableObject(DumpableObject *dobj, Archive *fout)
 static int
 dumpTableData_copy(Archive *fout, const void *dcontext)
 {
-	TableDataInfo *tdinfo = (TableDataInfo *) dcontext;
-	TableInfo  *tbinfo = tdinfo->tdtable;
+	const TableDataInfo *tdinfo = dcontext;
+	const TableInfo *tbinfo = tdinfo->tdtable;
 	const char *classname = tbinfo->dobj.name;
 	PQExpBuffer q = createPQExpBuffer();
 
@@ -2548,8 +2548,8 @@ dumpTableData_copy(Archive *fout, const void *dcontext)
 static int
 dumpTableData_insert(Archive *fout, const void *dcontext)
 {
-	TableDataInfo *tdinfo = (TableDataInfo *) dcontext;
-	TableInfo  *tbinfo = tdinfo->tdtable;
+	const TableDataInfo *tdinfo = dcontext;
+	const TableInfo *tbinfo = tdinfo->tdtable;
 	DumpOptions *dopt = fout->dopt;
 	PQExpBuffer q = createPQExpBuffer();
 	PQExpBuffer insertStmt = NULL;
@@ -2619,7 +2619,7 @@ dumpTableData_insert(Archive *fout, const void *dcontext)
 		 */
 		if (insertStmt == NULL)
 		{
-			TableInfo  *targettab;
+			const TableInfo *targettab;
 
 			insertStmt = createPQExpBuffer();
 
@@ -2871,7 +2871,7 @@ static void
 dumpTableData(Archive *fout, const TableDataInfo *tdinfo)
 {
 	DumpOptions *dopt = fout->dopt;
-	TableInfo  *tbinfo = tdinfo->tdtable;
+	const TableInfo *tbinfo = tdinfo->tdtable;
 	PQExpBuffer copyBuf = createPQExpBuffer();
 	PQExpBuffer clistBuf = createPQExpBuffer();
 	DataDumperPtr dumpFn;
@@ -2892,7 +2892,7 @@ dumpTableData(Archive *fout, const TableDataInfo *tdinfo)
 		(dopt->load_via_partition_root ||
 		 forcePartitionRootLoad(tbinfo)))
 	{
-		TableInfo  *parentTbinfo;
+		const TableInfo *parentTbinfo;
 		char	   *sanitized;
 
 		parentTbinfo = getRootTableInfo(tbinfo);