PowerD.html - Function using

Description:
PowerD can use currently three types of functions, first are library functions, second are procedures and third are linked library functions. Each of these is defined in other way, but they all can be used alike. Functions can be stand alone like:
```
  Function(a,b,c)
```
or functions, that returns one or more values:
```
  x:=Function(a,b,c)
  x,y,z:=Function(a,b,c)
```