Unify thread pool logic across the rest of the compiler, using a global thread pool

src/common.cpp

@@ -44,11 +44,9 @@ void debugf(char const *fmt, ...);
 #include "queue.cpp"
 #include "common_memory.cpp"
 #include "string.cpp"
-
-
-
 #include "range_cache.cpp"
 
+
 u32 fnv32a(void const *data, isize len) {
 	u8 const *bytes = cast(u8 const *)data;
 	u32 h = 0x811c9dc5;