The SELECT INTO OUTFILE FIELDS ENCLOSED BY digit or minus sign,
followed by the same LOAD DATA INFILE statement, used wrond encoding
of non-string fields contained the enclosed character in their text
representation.

Example:
  SELECT 15, 9 INTO OUTFILE 'text' FIELDS ENCLOSED BY '5';

Old encoded result in the text file:
  5155 595
         ^ was decoded as the 1st enclosing character of the 2nd field;
        ^ was skipped as garbage;
  ^    ^ was decoded as a pair of englosing characters of the 1st field;
      ^   was decoded as traling space of the first field;
    ^^ was decoded as a doubled enclosed character.

New encoded result in the text file:
  51\55 595
  ^   ^ pair of enclosing characters of the 1st field;
    ^^ escaped enclosed character.



sql/sql_class.h:
  Fixed bug #29442.
  The NUMERIC_CHARS macro constant has been defined to enumerate
  all possible characters of a numeric value text representation.
  The select_export::is_unsafe_field_sep boolean flag has been added
  to apply the encoding algorithm to non-string values when it is
  necessary.
sql/sql_class.cc:
  Fixed bug #29442.
  The select_export::send_data method has been modified to encode text
  representation of fields of all data types like string fields.
mysql-test/t/loaddata.test:
  Updated test case for bug #29442.
mysql-test/r/loaddata.result:
  Updated test case for bug #29442.