Remove inappropriate inclusions of c.h and postgres_fe.h.

Per our usual policy, Postgres header files should not include these;
the decision as to which one to use is to be made in the calling .c
file instead.

These errors aren't particularly new, but I'm not feeling a need
to back-patch these changes; it's mostly just neatnik-ism.

src/bin/pg_combinebackup/copy_file.h

@@ -11,7 +11,6 @@
 #ifndef COPY_FILE_H
 #define COPY_FILE_H
 
-#include "c.h"
 #include "common/checksum_helper.h"
 
 /*

src/include/fe_utils/option_utils.h

@@ -12,8 +12,6 @@
 #ifndef OPTION_UTILS_H
 #define OPTION_UTILS_H
 
-#include "postgres_fe.h"
-
 #include "common/file_utils.h"
 
 typedef void (*help_handler) (const char *progname);

src/include/fe_utils/query_utils.h

@@ -12,8 +12,6 @@
 #ifndef QUERY_UTILS_H
 #define QUERY_UTILS_H
 
-#include "postgres_fe.h"
-
 #include "libpq-fe.h"
 
 extern PGresult *executeQuery(PGconn *conn, const char *query, bool echo);