Move carefully obscured SunOS 4 specific #include out of c.h into port

header file.  SunOS 4 is probably broken anyway, but this item stuck out as
completely weird.

src/include/c.h

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/c.h,v 1.231 2008/12/11 07:34:08 petere Exp $
+ * $PostgreSQL: pgsql/src/include/c.h,v 1.232 2008/12/11 09:17:07 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -769,10 +769,6 @@ typedef NameData *Name;
 #define PG_BINARY_W "w"
 #endif
 
-#if defined(sun) && defined(__sparc__) && !defined(__SVR4)
-#include <unistd.h>
-#endif
-
 /* These are for things that are one way on Unix and another on NT */
 #define NULL_DEV		"/dev/null"
 

src/include/port/sunos4.h

@@ -1,5 +1,7 @@
 /*
- * $PostgreSQL: pgsql/src/include/port/sunos4.h,v 1.10 2008/05/17 01:28:24 adunstan Exp $ 
+ * $PostgreSQL: pgsql/src/include/port/sunos4.h,v 1.11 2008/12/11 09:17:07 petere Exp $ 
  *
  * sprintf() returns char *, not int, on SunOS 4.1.x */
 #define SPRINTF_CHAR
+
+#include <unistd.h>