[boost] Boost.Thread and extensibility

Hi, I've been continuing my quest to try and use Boost for my DSP and its C++ compiler. I've been looking at Boost.Thread and it seems that it relies on one of a fixed few threading libraries to exist. I have my own native implementation of mutexes etc. and it doesn't seem like there is any easy way to plug it in without editing a lot of the boost source. Is this an issue that has been raised before? Thanks Andrew