Refactor some code

- Write tests for cthreads
- Fix bugs in pe2.com tool
- Fix ASAN issue with GetDosEnviron()
- Consolidate the cthread header files
- Some code size optimizations for MODE=
- Attempted to squash a tls linker warning
- Attempted to get futexes working on FreeBSD

libc/intrin/gettid.greg.c

@@ -58,7 +58,7 @@ privileged int gettid(void) {
   struct WinThread *wt;
 
   if (__tls_enabled) {
-    rc = *(int *)(__get_tls() + 0x38);
+    rc = *(int *)(__get_tls_inline() + 0x38);
     return rc;
   }