Fix a passel of recently-committed violations of the rule 'thou shalt

have no other gods before c.h'.  Also remove some demonstrably redundant
#include lines, mostly of <errno.h> which was added to c.h years ago.

src/backend/port/dynloader/aix.c

@@ -6,7 +6,6 @@
 
 #include "postgres.h"
 
-#include <errno.h>
 #include "sys/ldr.h"
 #include <a.out.h>
 #include "ldfcn.h"