On the fsfs-format7 branch:  Make zlib compression and associated
functionality generally available, i.e. move it from lib_delta to
lib_subr.  The reason is that the use of zlib compression is no
longer restricted to txdelta and the trigger is that I just wrote
yet another user of it that is non-txdelta.

While at it, rephrase the API such that other compression methods
may be provided through the same interface in the future.

* subversion/include/private/svn_delta_private.h
  (svn__compress,
   svn__decompress): move API declaration from here ...

* subversion/include/private/svn_subr_private.h
  (svn__compress,
   svn__decompress): ... to here
  (SVN__MAX_ENCODED_UINT_LEN,
   SVN__COMPRESSION_NONE,
   SVN__COMPRESSION_ZLIB_MIN,
   SVN__COMPRESSION_ZLIB_DEFAULT,
   SVN__COMPRESSION_ZLIB_MAX): new constants, inspired by similar
                               ones in lib_delta
  (svn__encode_uint,
   svn__decode_uint): publish former lib_delta-private functions

* subversion/include/svn_error_codes.h
  (SVN_ERR_BAD_COMPRESSION_METHOD): define new error code

* subversion/libsvn_delta/svndiff.c
  (MAX_ENCODED_INT_LEN,
   encode_int,
   decode_int): superseded by lib_subr API
  (MAX_INSTRUCTION_LEN,
   append_encoded_int,
   send_simple_insertion_window,
   window_handler,
   decode_file_offset,
   decode_size,
   count_and_verify_instructions,
   write_handler): update API users
  (svnCompressBound,
   MIN_COMPRESS_SIZE,
   zlib_encode,
   zlib_decode,
   svn__compress,
   svn__decompress): move from here ...

* subversion/libsvn_subr/compress.c
  (svnCompressBound,
   MIN_COMPRESS_SIZE,
   zlib_encode,
   zlib_decode,
   svn__compress,
   svn__decompress): ... to here; refine
  (svn__encode_int,
   svn__decode_int): moved here; tuned

* subversion/libsvn_fs_fs/revprops.c
  (parse_packed_revprops,
   repack_revprops,
   copy_revprops): update API users


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1461851 13f79535-47bb-0310-9956-ffa450edef68