/**
 * Return the symbolic name of an error code.  If the error code
 * is in svn_error_codes.h, return the name of the macro as a string.
 * If the error number is not recognised, return @c NULL.
 *
 * An error number may not be recognised because it was defined in a future
 * version of Subversion (e.g., a 1.9.x server may transmit a defined-in-1.9.0
 * error number to a 1.8.x client).
 *
 * An error number may be recognised @em incorrectly if the @c apr_status_t
 * value originates in another library (such as libserf) which also uses APR.
 * (This is a theoretical concern only: the @c apr_err member of #svn_error_t
 * should never contain a "foreign" @c apr_status_t value, and
 * in any case Subversion and Serf use non-overlapping subsets of the
 * @c APR_OS_START_USERERR range.)
 *
 * Support for error codes returned by APR itself (i.e., not in the
 * @c APR_OS_START_USERERR range, as defined in apr_errno.h) may be implemented
 * in the future.
 *
 * @note In rare cases, a single numeric code has more than one symbolic name.
 * (For example, #SVN_ERR_WC_NOT_DIRECTORY and #SVN_ERR_WC_NOT_WORKING_COPY).
 * In those cases, it is not guaranteed which symbolic name is returned.
 *
 * @since New in 1.8.
 */
const char *
svn_error_symbolic_name(apr_status_t statcode);