I found a variant of this solution (for the php_intl.dll problem), where you don't need to copy all icu*46.dll files, but only three of them, in this article:
As shown there, you need only to copy icudt46.dll , icuin46.dll and icuuc46.dll to apache/bin folder
When I copied all icu*46.dll files, the apache refused to work, in fact.
Another solution that solved the problem, without the need of copying this files to apache/bin, was adding the php path C:\Xampp\php to the system variable PATH, as suggested in:
Note: I am using Xampp 1.8.1 where this problem, unfortunately, still remains.