Remove real type

[Don]

BCS wrote:
> Hello bearophile,
> 
>> Even if you are right, real-life programs often need to process good
>> amounts of memory, so using reals they are slower.
> 
> Exactly, that is the one case where float and double are better, where 
> large volumes of data need to be processed, normally in a regular 
> fashion. For cases where small amounts of data are processed and where 
> there is littler opportunity to use vectorization, they have little or 
> no advantage over real.
> 
> And I suspect that both kinds of code occur with some regularity.
> 

A simple rule of thumb: if it's an array, use float or double. If it's 
not, use real.