Completed documenting the syntax in BNF

git-svn-id: http://svn.code.sf.net/p/angelscript/code@2075 404ce1b2-830e-0410-a2e2-b09542c77caf
Reduced overhead in CallSystemFunction

git-svn-id: http://svn.code.sf.net/p/angelscript/code@2076 404ce1b2-830e-0410-a2e2-b09542c77caf