Improve option-parsing error messages from the internal diff: report which option was bad, and don't mention the command line.
Improve option-parsing error messages from the internal diff: report which
option was bad, and don't mention the command line.

An example, assuming the config file contains "diff-extensions = -U6 -p":

Before this patch:
  $ svn diff --internal-diff
  svn: Error parsing diff options: Bad character specified on command line

After this patch:
  $ svn diff --internal-diff
  svn: Error in options to internal diff
  svn: invalid option character: U

* subversion/libsvn_diff/diff_file.c
  (opt_parsing_error_baton_t): New struct.
  (opt_parsing_error_func): New function.
  (svn_diff_file_options_parse): Use opt_parsing_error_func() to capture any
    error message produced by apr_getopt_long(), and use that message if
    parsing fails. Avoid using messages that refer to a "command line".

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion