types got intertwined, has been fixed;
** the type system is now able to reason about the interaction
between INTEGER and RATIO types more completely;
+ * fixed CEILING optimization for a divisor of form 2^k.
+ * fixed bug 240 (emitting extra style warnings "using the lexical
+ binding of the symbol *XXX*" for &OPTIONAL arguments). (reported
+ by Antonio Martinez)
planned incompatible changes in 0.7.x:
* (not done yet, but planned:) When the profiling interface settles