Fix issue #4340, "fs layer should reject filenames with trailing \n",
by making the FS layer reject new paths which contain control characters.

To some degree, this change breaks compatibility with the officially
documented rules for path names in the FS API (see svn_fs.h, the
comment starting with "Directory entry names and directory paths")

However, given the impracticalities of managing repositories which contain
paths with control characters such as \n (see dev@ thread linked from
issue #4340), I don't expect this to really hurt anyone. Subversion clients
have never allowed paths containing control characters to be added to version
control, so I decided not to single out \n during server-side validation.

* subversion/libsvn_fs/editor.c
  (can_create): Reject paths containing control characters.

* subversion/libsvn_fs/fs-loader.c
  (svn_fs__path_valid): Reject paths containing control characters.

* subversion/tests/libsvn_fs/fs-test.c
  (test_funcs): Remove XFAIL marker from filename_trailing_newline test.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1461580 13f79535-47bb-0310-9956-ffa450edef68