1521 – Ambiguous documentation

The documentation currently reads as follows:
Class instances are normally allocated on the garbage collected heap. However, if they:
 * are allocated as local symbols in a function
 * are allocated using new
 * use new with no arguments
 * have the scope storage class
It's umbiguous if all items of the list are required as condition, or only one of them.
The chapter should be rephrased to make clear that all conditions have to me true before the object is put on stack ("and" nor "or").

Commit pushed to https://github.com/D-Programming-Language/d-programming-language.org
https://github.com/D-Programming-Language/d-programming-language.org/commit/3d22dec01aac1c6a436fb82849fba49411f9e97e
fix Issue 1521 - Ambiguous documentation