0xFF is internal separator for SET|ENUM names. 
If this symbol is present in SET|ENUM names then we replace it with 
','(deprecated symbol for SET|ENUM names) during frm creation
and restore to 0xFF during frm opening


mysql-test/r/type_enum.result:
  Bug#20922 mysql removes a name of first column in a table
  test case
mysql-test/t/type_enum.test:
  Bug#20922 mysql removes a name of first column in a table
  test case
sql/table.cc:
  Bug#20922 mysql removes a name of first column in a table
  Replace all ',' symbols with NAMES_SEP_CHAR in interval names.
sql/unireg.cc:
  Bug#20922 mysql removes a name of first column in a table
  if NAMES_SEP_CHAR symbols are present in interval name
  then replace all NAMES_SEP_CHAR symbols with ','