[svn r341] Fix all regressions between [332] and [340]: - fixed assert on empty catch body - fixed(?) typedefed classes in catch specification - fixed assert with catchall Added some documentation.

module bug1;
struct Foo { Foo opSub(ref Foo b) { return Foo(); } }
struct Bar { Foo whee; }
void test(ref Bar moo) { Foo nngh; auto plonk = nngh - moo.whee; }
void main() { Bar bar; test(bar); }