Remove complex and imaginary types?

[Walter Bright]

The issue comes up now and then about why have complex and imaginary 
types, rather than using structs? All but one of the advantages of 
having them be core types can be addressed with advancing compiler 
technology. Getting rid of them will release 6 keywords, and make the 
core language simpler. Given the increasing complexity of D, this will help.

The remaining advantage is that of imaginary literals, i.e. the i postfix:

	3 + 5i

Assuming we solve the literal problem, existing code would only need to add:

	import std.complex;

to acquire complex and imaginary types.