On the thunder branch:  Replace the PATH+LOCATION identification
for the access location by a simple KEY.

The caller already had to combine various bits of information to
construct the "path" element, so adding one more is no extra burden.
Also, it makes the arbitrary nature of the location identifier more
apparent to the user.

* subversion/include/private/svn_fs_util.h
  (svn_fs__thunder_begin_access): Replace PATH+LOCATION by KEY.

* subversion/libsvn_fs_util/thunder.c
  (construct_key): No longer needed.
  (svn_fs__thunder_begin_access): Convert incoming key to a svn_stringbuf_t
                                  to match our internal representation.

* subversion/libsvn_fs_fs/util.c
  (svn_fs_fs__thundered_cache_get,
   svn_fs_fs__thundered_cache_get_partial): Construct the full key here now.

* subversion/libsvn_fs_fs/cached_data.c
  (block_read): Same.

* subversion/tests/libsvn_fs/fs-test.c
  (basic_thunder_interface): Update test case.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/thunder@1586768 13f79535-47bb-0310-9956-ffa450edef68