Make improvements

- Improve compatibility with Blink virtual machine
- Add non-POSIX APIs for joining threads and signal masks
- Never ever use anything except 32-bit integers for atomics
- Add some `#undef` statements to workaround `ctags` problems

libc/intrin/mmi_lock.c

@@ -20,14 +20,22 @@
 #include "libc/str/str.h"
 #include "libc/thread/thread.h"
 
+#ifdef __mmi_lock
+#undef __mmi_lock
+#endif
+
+#ifdef __mmi_unlock
+#undef __mmi_unlock
+#endif
+
 // this lock currently needs to be (1) recursive and (2) not nsync
 
 extern pthread_mutex_t __mmi_lock_obj;
 
-void(__mmi_lock)(void) {
+void __mmi_lock(void) {
   pthread_mutex_lock(&__mmi_lock_obj);
 }
 
-void(__mmi_unlock)(void) {
+void __mmi_unlock(void) {
   pthread_mutex_unlock(&__mmi_lock_obj);
 }