code can use it. This takes a single constant argument and fails to compile
if it is 0 (false). The main application of this is to make assertions about
structure sizes at compile time, in order to validate assumptions made in
other code. Examples:
CTASSERT(sizeof(struct foo) == FOO_SIZEOF);
CTASSERT(sizeof(struct foo) == (1 << FOO_SHIFT));
Requested by: jhb, phk
d86b2422b9