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/fds_lock.c

@@ -20,11 +20,19 @@
 #include "libc/str/str.h"
 #include "libc/thread/thread.h"
 
-void(__fds_lock)(void) {
+#ifdef __fds_lock
+#undef __fds_lock
+#endif
+
+#ifdef __fds_unlock
+#undef __fds_unlock
+#endif
+
+void __fds_lock(void) {
   pthread_mutex_lock(&__fds_lock_obj);
 }
 
-void(__fds_unlock)(void) {
+void __fds_unlock(void) {
   pthread_mutex_unlock(&__fds_lock_obj);
 }