* Minor code refactoring of atomic_ops.c, generic_pthread.h.
* Minor configure build improvements (e.g., ensure proper autoconf version).
* Place only major per-release changes description to ChangeLog (this file).
+* Recognize AO_PREFER_GENERALIZED macro to favor generalization over assembly.
* Remove all auto-generated files except for generalize-small.h from the repo.
* Remove duplicate doc/COPYING and empty NEWS files.
* Replace atomic_ops_malloc static mmap-related empty functions with macros.