slow & highly contentious implementation of barriers using more basic sync primitives; fall back if sync barriers not present in win32 version

src/raddbg/raddbg_main.c

@@ -10,11 +10,11 @@
 // [ ] value coloring view in watch window, so you can quickly scroll & see values outside of a threshold
 // [x] step out of scopes / loops
 //
-// [x] policy for closing debug info which is no longer relevant?
 // [ ] codebase-internal barrier impl (win7/linux support)
 // [ ] asan pass
 // [ ] external window focusing bugs
 // [ ] PDB -> RDI conversion memory usage
+// [x] policy for closing debug info which is no longer relevant?
 // [x] killing/restarting thread performance (#780)
 //
 // [ ] project/user file improvements