Make sure that attack speed is calculated correctly

[ark120202]

Fixed a longstanding bug that caused units to attack more slowly than expected at certain attack speeds.

Should be checked how it works with https://github.com/ark120202/angel-arena-black-star/commit/fb3bac4aab58ba6114e4fbcf8868cde9b61c3dcc

Reference:

• http://www.dota2.com/news/updates/45375/
• https://github.com/SteamDatabase/GameTracking-Dota2/commit/e48659884c165708491b0b9efcfd72f7a89f5fd1#diff-0836cd787ef53d0c7df9e71808d57f67