Remove support for v11.

Standard Support for both EDB Postgres Advanced Server 11 and
PostgreSQL 11 is already ended.  Thus, adjust Makefile so that we
restrict compilation of mongo_fdw code against v11.  Update the README
accordingly.  Also, clean up the code for the same.

FDW-673, Suraj Kharage, reviewed by Sravan Velagandula, tested by
Ajaykumar Pal.

Makefile

@@ -42,6 +42,6 @@ ifndef MAJORVERSION
     MAJORVERSION := $(basename $(VERSION))
 endif
 
-ifeq (,$(findstring $(MAJORVERSION), 11 12 13 14 15 16))
-    $(error PostgreSQL 11, 12, 13, 14, 15, or 16 is required to compile this extension)
+ifeq (,$(findstring $(MAJORVERSION), 12 13 14 15 16))
+    $(error PostgreSQL 12, 13, 14, 15, or 16 is required to compile this extension)
 endif

README.md

@@ -5,7 +5,7 @@ This PostgreSQL extension implements a Foreign Data Wrapper (FDW) for
 [MongoDB][1].
 
 Please note that this version of mongo_fdw works with PostgreSQL and EDB
-Postgres Advanced Server 11, 12, 13, 14, 15 and 16.
+Postgres Advanced Server 12, 13, 14, 15 and 16.
 
 <img src="https://upload.wikimedia.org/wikipedia/commons/2/29/Postgresql_elephant.svg" align="center" height="100" alt="PostgreSQL"/>	+	<img src="https://www.tutorialsteacher.com/Content/images/home/mongodb.svg" align="center" height="100" alt="MongoDB"/>
 

deparse.c

@@ -25,13 +25,7 @@
 #endif
 #include "mongoc.h"
 #include "mongo_query.h"
-#if PG_VERSION_NUM < 120000
-#include "nodes/relation.h"
-#include "optimizer/var.h"
-#endif
-#if PG_VERSION_NUM >= 120000
 #include "optimizer/optimizer.h"
-#endif
 #include "parser/parsetree.h"
 #include "utils/rel.h"
 #include "utils/syscache.h"
@@ -677,9 +671,5 @@ mongo_is_foreign_pathkey(PlannerInfo *root, RelOptInfo *baserel,
 bool
 mongo_is_builtin(Oid oid)
 {
-#if PG_VERSION_NUM >= 120000
 	return (oid < FirstGenbkiObjectId);
-#else
-	return (oid < FirstBootstrapObjectId);
-#endif
 }