fix build under cygwin
Testsuite fix for duplicate definitions in emitted assembly file
Require linking in library for all files except D interface files.
Replace DCFG_SEMAPHORE_IMPL with cleaner DCFG_THREAD_MODEL
Add gcc.gthr implementation as a generic wrapper for internal thread support
Remove posix-specific Cxx11 gthreads, add win32 support
Implement gcc.emutls to handle TLS emulation on GDC
Implement gthreads recursive mutexes
Fix emutls for x32 and similar archs
Use gthreads for critical/monitor implementations
Assume AIX is _THREAD_SAFE and Lynx is _MULTITHREADED