On the fsfs-format7 branch:  Fix bugs in the string table implemenation
discovered by our new unit tests.

* subversion/libsvn_fs_fs/string_table.c
  (insert_string): buggy remaining table capacity calculation
  (svn_fs_fs__string_table_builder_add): the default match length is 0
  (create_table): pick delta base from tree order not insert order
  (table_copy_string): handle an edge case
  (svn_fs_fs__string_table_get): result got lost


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1451738 13f79535-47bb-0310-9956-ffa450edef68