Rewritten call to arms update function.

git-svn-id: http://keeperfx.googlecode.com/svn/trunk@1480 40a56aae-0377-11df-bfb3-7781b9cb07ea
Modified computer player to not create two tasks which require power hand at the same time.

git-svn-id: http://keeperfx.googlecode.com/svn/trunk@1481 40a56aae-0377-11df-bfb3-7781b9cb07ea