bytes length.

The server has been modified to report warnings on truncation to
65536 bytes as usual.



sql/sql_string.cc:
  Fixed bug #32282.
  The well_formed_copy_nchars function returned an incorrect value
  of copied bytes of the truncated input string: extra length of
  the first truncated character added to the *from_end_pos pointer.
  That has been fixed.
mysql-test/r/type_blob.result:
  Added test case for bug #32282.
mysql-test/t/type_blob.test:
  Added test case for bug #32282.