Fix a whole bunch of #includes that were either wrong or redundant.

The first rule of portability for us is 'thou shalt have no other gods
before c.h', and a whole lot of these files were either not including
c.h at all, or including random system headers beforehand, either of
which sins can mess up largefile support nicely.  Once you have
included c.h, there is no need to re-include what it includes, either.

src/port/thread.c

@@ -7,15 +7,13 @@
  *
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/port/thread.c,v 1.29 2004/12/31 22:03:53 pgsql Exp $
+ * $PostgreSQL: pgsql/src/port/thread.c,v 1.30 2005/07/28 04:03:14 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 
 #include "c.h"
 
-#include <sys/types.h>
-#include <errno.h>
 #ifdef WIN32_CLIENT_ONLY
 #undef ERROR
 #else
@@ -25,6 +23,7 @@
 #include <pthread.h>
 #endif
 
+
 /*
  *	Threading sometimes requires specially-named versions of functions
  *	that return data in static buffers, like strerror_r() instead of