Revision 1503010

svn_utf_*: Improve error handling.

This is part of a patch I posted recently.  The remaining part --- handling
APR_EINVAL and APR_ENOTIMPL as fatal errors --- may be committed separately
(for ease of backporting).

* subversion/libsvn_subr/utf.c
  (xlate_alloc_handle): Tweak the error handling so that apr_strerror() of the
    error code is included in the error chain, in addition to the custom error
    added here.  The previous code would report error codes such as E70023
    (although not that particular error which is caught and ignored) but mere
    mortals aren't supposed to know what errno error that maps to.  The new
    code would, if the error was not ignored, report:

      svn: E200001: Can't create a character converter from native encoding to 'UTF-8'
      svn: E070023: This function has not been implemented on this platform