Casts in tinytest macros suppress useful warnings

In the tinytest tt_assert_test_fmt_type macro, we do:

	type val1_ = (type) (a);						\
	type val2_ = (type) (b);						\

Those two typecasts are dangerous, since they suppress every signed/unsigned warning, narrowing warning, or whatever that would create a problem in our unit tests. We should take them out and clean up the mess.

Putting this in 0.2.5.x since working unit tests will help us find other bugs, maybe.