Double free issue on PosixThreadSupport.cpp

[ymhsieh]

Hello,

I believe there is an issue in BulletMultiThreaded/PosixThreadSupport.cpp.

After tracing the code, I concluded that
1. the PosixThreadSupport::stopSPU() is called by the SpuCollisionTaskProcess::~SpuCollisionTaskProcess()
2. the PosixThreadSupport::stopSPU() is also called by PosixThreadSupport::~PosixThreadSupport()

As a result, the PosixThreadSupport::mainSemaphore got destroyed twice. And it causes some memory block to be freed twice.

[ymhsieh]

I have got it fixed. Can I submit a patch to bullet SVN?