Some fields (GEOMETRY first of all) can't be handled properly in this
case at all. So we return an error in this case

	specifying DEFAULT

This was not specific to datetime.  When there is no default value 
for a column, and the user inserted DEFAULT, we would write 
uninitialized memory to the table.  

Now, insist on writing a default value, a zero-ish value, the same 
one that comes from inserting NULL into a not-NULL field.

(This is, at best, really strange behavior that comes from allowing 
sloppy usage, and serves as a good reason always to run one's server 
in a strict SQL mode.)

Moved enabling of warnings to ensure that no warnings are generated
when this test case is executed on a clone where InnoDB is not
activated. This would fail the test case in those clones otherwise.