Change fmgr.h typedefs to use original names

fmgr.h defined some types such as fmNodePtr which is just Node *, but
it made its own types to avoid having to include various header files.
With C11, we can now instead typedef the original names without fear
of conflicts.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/10d32190-f31b-40a5-b177-11db55597355@eisentraut.org

src/backend/utils/fmgr/fmgr.c

@@ -1570,7 +1570,6 @@ InputFunctionCall(FmgrInfo *flinfo, char *str, Oid typioparam, int32 typmod)
  * This is basically like InputFunctionCall, but the converted Datum is
  * returned into *result while the function result is true for success or
  * false for failure.  Also, the caller may pass an ErrorSaveContext node.
- * (We declare that as "fmNodePtr" to avoid including nodes.h in fmgr.h.)
  *
  * If escontext points to an ErrorSaveContext, any "soft" errors detected by
  * the input function will be reported by filling the escontext struct and
@@ -1584,7 +1583,7 @@ InputFunctionCall(FmgrInfo *flinfo, char *str, Oid typioparam, int32 typmod)
 bool
 InputFunctionCallSafe(FmgrInfo *flinfo, char *str,
 					  Oid typioparam, int32 typmod,
-					  fmNodePtr escontext,
+					  Node *escontext,
 					  Datum *result)
 {
 	LOCAL_FCINFO(fcinfo, 3);
@@ -1639,7 +1638,7 @@ InputFunctionCallSafe(FmgrInfo *flinfo, char *str,
 bool
 DirectInputFunctionCallSafe(PGFunction func, char *str,
 							Oid typioparam, int32 typmod,
-							fmNodePtr escontext,
+							Node *escontext,
 							Datum *result)
 {
 	LOCAL_FCINFO(fcinfo, 3);