libsmartcols: support custom wrap and remove SCOLS_FL_WRAPNL

libsmartcols: support custom wrap and remove SCOLS_FL_WRAPNL

This new API provides full control on multi-line cells, you can wrap
text by new lines (build-in support) or by another way (after words,
commas, etc.) Changes:

* new scols_column_set_wrapfunc() sets pointers to two callback functions

   1/ chunksize() - returns largest data chunk size; used when we
                    calculate columns width
   2/ nextchunk() - terminate the current chunk and returns pointer to
                    the next; used when we print data

* remove SCOLS_FL_WRAPNL and add new functions scols_wrapnl_chunksize()
  and scols_wrapnl_nextchunk() to provide build-in functionality to
  wrap cells on \n

* remove scols_column_is_wrapnl() add scols_column_is_customwrap()
  (returns true if custom wrap functions are defined)

* add scols_column_set_safechars() and scols_column_get_safechars() to
  allow to control output encoding, safe chars are not encoded by \xFOO

* modify "fromfile" test code to use build-in scols_wrapnl_* callbacks
  for "wrapnl" tests

* add new function scols_column_get_table()

Signed-off-by: Karel Zak <kzak@redhat.com>