On the revprop-caching-ng branch: Remove the "named atomics" code.

* build.conf
  (msvc-export): Remove reference to feature header.
  (named_atomic-test,
   named_atomic-proc-test): Remove these test build targets.
  (__ALL_TESTS__): No longer depend on the above.

* configure.ac
  (BUILD_RULES): There is no "sub-test" install target anymore.

* subversion/include/private/svn_named_atomic.h,
  subversion/libsvn_subr/named_atomic.c:
  Remove the feature implementation.

* subversion/tests/libsvn_subr/named_atomic-test.c,
  subversion/tests/libsvn_subr/named_atomic-test-common.h,
  subversion/tests/libsvn_subr/named_atomic-test-proc.c:
  Remove the test source code.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/revprop-caching-ng@1620599 13f79535-47bb-0310-9956-ffa450edef68