Use std::recursive_mutex when EASTL_CPP11_MUTEX_ENABLED is defined

[Jasper-Bekkers]

Hi,

This tweet https://twitter.com/jdryg/status/698042963604144128 and this one https://twitter.com/jdryg/status/698043020046921730 from Jim Drygiannakis seem to suggest it might be a good idea / preferable to use std::recursive_mutex instead of std::mutex as a fallback for eastl::mutex, since the implementations (both Windows & pthreads) of eastl::mutex seems to use recusive locking.

I can't recall off the top of my head if eastl::mutex was always recursive, but I think it is / was on other platforms. What do you guys think?

[rparolin]

EASTL doesn't implement any of the std::concurrency in the standard. It implements enough for an internal API that drives features like eastl::shared_ptr. Using a std::recursive_mutex would be preferable as long its available for use on all compilers.