Fix some typos with {a,an}

One of the changes impacts the documentation, so backpatch.

Author: Peter Smith
Discussion: https://postgr.es/m/CAHut+Pu6+c+r3mY24VT7u+H+E_s6vMr5OdRiZ8NT3EOa-E5Lmw@mail.gmail.com
Backpatch-through: 14

contrib/amcheck/verify_nbtree.c

@@ -1512,7 +1512,7 @@ bt_target_page_check(BtreeCheckState *state)
 	/*
 	 * Special case bt_child_highkey_check() call
 	 *
-	 * We don't pass an real downlink, but we've to finish the level
+	 * We don't pass a real downlink, but we've to finish the level
 	 * processing. If condition is satisfied, we've already processed all the
 	 * downlinks from the target level.  But there still might be pages to the
 	 * right of the child page pointer to by our rightmost downlink.  And they

doc/src/sgml/ecpg.sgml

@@ -6977,7 +6977,7 @@ EXEC SQL CLOSE cursor_name;
     <title>Compatibility</title>
 
     <para>
-     <command>DECLARE STATEMENT</command> is a extension of the SQL standard,
+     <command>DECLARE STATEMENT</command> is an extension of the SQL standard,
      but can be used in famous DBMSs.
     </para>
    </refsect1>

src/backend/access/table/toast_helper.c

@@ -33,7 +33,7 @@
  * All of these arrays should have a length equal to tupleDesc->natts.
  *
  * On return, toast_flags and toast_attr will have been initialized.
- * toast_flags is just a single uint8, but toast_attr is an caller-provided
+ * toast_flags is just a single uint8, but toast_attr is a caller-provided
  * array with a length equal to tupleDesc->natts.  The caller need not
  * perform any initialization of the array before calling this function.
  */

src/backend/catalog/pg_depend.c

@@ -176,7 +176,7 @@ recordMultipleDependencies(const ObjectAddress *depender,
  * Passing false is a guarantee that the object is newly created, and so
  * could not already be a member of any extension.
  *
- * Note: isReplace = true is typically used when updating a object in
+ * Note: isReplace = true is typically used when updating an object in
  * CREATE OR REPLACE and similar commands.  The net effect is that if an
  * extension script uses such a command on a pre-existing free-standing
  * object, the object will be absorbed into the extension.  If the object

src/backend/jit/llvm/llvmjit_error.cpp

@@ -84,7 +84,7 @@ llvm_leave_fatal_on_oom(void)
 }
 
 /*
- * Are we currently in an fatal-on-oom section? Useful to skip cleanup in case
+ * Are we currently in a fatal-on-oom section? Useful to skip cleanup in case
  * of errors.
  */
 bool

src/backend/replication/logical/reorderbuffer.c

@@ -452,7 +452,7 @@ ReorderBufferReturnTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
 }
 
 /*
- * Get an fresh ReorderBufferChange.
+ * Get a fresh ReorderBufferChange.
  */
 ReorderBufferChange *
 ReorderBufferGetChange(ReorderBuffer *rb)
@@ -558,7 +558,7 @@ ReorderBufferGetTupleBuf(ReorderBuffer *rb, Size tuple_len)
 }
 
 /*
- * Free an ReorderBufferTupleBuf.
+ * Free a ReorderBufferTupleBuf.
  */
 void
 ReorderBufferReturnTupleBuf(ReorderBuffer *rb, ReorderBufferTupleBuf *tuple)
@@ -639,7 +639,7 @@ ReorderBufferTXNByXid(ReorderBuffer *rb, TransactionId xid, bool create,
 	}
 
 	/*
-	 * If the cache wasn't hit or it yielded an "does-not-exist" and we want
+	 * If the cache wasn't hit or it yielded a "does-not-exist" and we want
 	 * to create an entry.
 	 */