CREATE TABLE t2 SELECT t1.column1 FROM t1;
used to copy the DEFAULT of t1.column1 into t2.column1 except if this DEFAULT was
a function (CURRENT_TIMESTAMP); this exception is removed.
CREATE TABLE t2 (extra_column TIMESTAMP DEFAULT CURRENT_TIMESTAMP) SELECT t1.column1 FROM t1;
used to set extra_column to a zero date when inserting rows; now it sets it
to the current timestamp.
Both behaviors were in contradiction with 
http://dev.mysql.com/doc/refman/5.6/en/create-table-select.htm