Re: WIP: Access method extendability

Some notices:

1) create-am.3.patch.gz
  As I understand, you didn't add schema name to access method. Why? Suppose, if we implement SQL-like interface for AM screation/dropping then we should provide a schema qualification for them

2) create-am.3.patch.gz get_object_address_am()
+       switch (list_length(objname))
...
+               case 2:
+                       catalogname = strVal(linitial(objname));
+                       amname = strVal(lthird(objname));
                                        ^^^^^^ seems, it should be lsecond()

3) create-am.3.patch.gz
 Suppose, RM_GENERIC_ID is part of generic-xlog.3.patch.gz

4) Makefile(s)
As I can see, object files are lexicographically ordered

5) gindesc.c -> genericdesc.c in file header

6) generic-xlog.3.patch.gz
I don't like an idea to split START_CRIT_SECTION and END_CRIT_SECTION to GenericXLogStart and GenericXLogFinish. User's code could throw a error or allocate memory between them and error will become a panic.