Fix assorted inconsistent function declarations.

While gcc doesn't complain if you declare a function "static" and then
define it not-static, other compilers do; and in any case the code is
highly misleading this way.  Add the missing "static" keywords to a
couple of recent patches.  Per buildfarm member pademelon.

src/bin/pg_rewind/parsexlog.c

@@ -229,7 +229,7 @@ findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, TimeLineID tli,
 }
 
 /* XLogreader callback function, to read a WAL page */
-int
+static int
 SimpleXLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr,
 				   int reqLen, XLogRecPtr targetRecPtr, char *readBuf,
 				   TimeLineID *pageTLI)