Bug#11758543 50756: BIGINT '100' MATCHES 1.001E2

Expressions of the form
      BIGINT_COL <compare> <non-integer constant>

      should be done either as decimal, or float.

      Currently however, such comparisons are done as int,
      which means that the constant may be truncated,
      and yield false positives/negatives for all queries
      where compare is '>' '<' '>=' '<=' '=' '!='.

      BIGINT_COL IN <list of contstants>
      and
      BIGINT_COL BETWEEN <constant> AND <constant>
      are also affected.



mysql-test/r/bigint.result:
  New tests.
mysql-test/r/func_in.result:
  BIGINT <=> string comparison should be done as float,
  so a warning for the value 'abc' is appropriate.
mysql-test/t/bigint.test:
  New tests.
sql/item_cmpfunc.cc:
  In convert_constant_item() we verify that the constant item
  can be stored in the given field.
  For BIGINT columns (MYSQL_TYPE_LONGLONG) we must verify that the
  stored constant value is actually comparable as int,
  i.e. that the value was not truncated.
  
  For between: compare as int only if both arguments convert correctly to int.