makefile fixed for fmgr.h

Makefile fixed for fmgr.h

This gets us a clean compile of 'common' and 'gist' with *clean* #include
files

Change #include "" to #include <>

Remove a few unused #includes

Make sure it compiles with -Wall -Werror

Pointed out by Keith Parks

Note.  all include files that have been hit so far have had extraneous
       include files cleaned out and are reduced to...the lowest common
       "include file", based on 'cc -Wall -I. test.c', where test.c is:

#include "postgres.h"
#include "<top of branches>" (ie. top of branches this time was utils/fcache2.h)

working on it)

that it depends on

not