Allow passing jvm args via jvm.config or build.properties to ASC 2.0

The ASC 2.0 installation doesn't include a jvm.config file in the bin/ directory, but this seems like the only viable way to pass in java memory opts. Once I made this change, added the jvm.config, and rebuilt FDBuild, everything was happy.

Here's the related explanation: http://www.flashdevelop.org/community/viewtopic.php?f=13&t=11608&sid=a1f331524e0f14270fe312219f0bb56d