Move interrupt checking from ExecProcNode() to executor nodes.

In a followup commit ExecProcNode(), and especially the large switch
it contains, will largely be replaced by a function pointer directly
to the correct node. The node functions will then get invoked by a
thin inline function wrapper. To avoid having to include miscadmin.h
in headers - CHECK_FOR_INTERRUPTS() - move the interrupt checks into
the individual executor routines.

While looking through all executor nodes, I noticed a number of
arguably missing interrupt checks, add these too.

Author: Andres Freund, Tom Lane
Reviewed-By: Tom Lane
Discussion:
    https://postgr.es/m/22833.1490390175@sss.pgh.pa.us

src/backend/executor/nodeLockRows.c

@@ -26,6 +26,7 @@
 #include "executor/executor.h"
 #include "executor/nodeLockRows.h"
 #include "foreign/fdwapi.h"
+#include "miscadmin.h"
 #include "storage/bufmgr.h"
 #include "utils/rel.h"
 #include "utils/tqual.h"
@@ -44,6 +45,8 @@ ExecLockRows(LockRowsState *node)
 	bool		epq_needed;
 	ListCell   *lc;
 
+	CHECK_FOR_INTERRUPTS();
+
 	/*
 	 * get information from the node
 	 */