We frequently use property name constants in conjunction with hash containers. Provide new wrappers around apr_hash_get and apr_hash_set that accept such string constants and statically determine their size. That minimizes the hash access costs.
Mass change hash get and set calls for SVN_PROP_* constants.
* subversion/include/svn_hash.h (svn_hash_gets, svn_hash_sets): Doxygen-ize the docstring (svn_hash_gets_fixed_key, svn_hash_sets_fixed_key): define new apr_hash_* wrapper
* subversion/libsvn_client/add.c (svn_client__get_all_auto_props): use faster hash wrappers with SVN_PROP_*