Reduce header complexity

- Remove most __ASSEMBLER__ __LINKER__ ifdefs
- Rename libc/intrin/bits.h to libc/serialize.h
- Block pthread cancelation in fchmodat() polyfill
- Remove `clang-format off` statements in third_party

third_party/nsync/mem/array.c

@@ -18,7 +18,6 @@
 #include "libc/mem/mem.h"
 #include "libc/str/str.h"
 #include "third_party/nsync/array.internal.h"
-// clang-format off
 
 void a_ensure_ (void *v, int delta, int sz) {
 	typedef A_TYPE (void *) a_void_ptr;

third_party/nsync/mem/nsync_counter.c

@@ -31,7 +31,6 @@ asm(".ident\t\"\\n\\n\
 *NSYNC (Apache 2.0)\\n\
 Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
-// clang-format off
 
 /* Internal details of nsync_counter. */
 struct nsync_counter_s_ {

third_party/nsync/mem/nsync_cv.c

@@ -35,7 +35,6 @@ asm(".ident\t\"\\n\\n\
 *NSYNC (Apache 2.0)\\n\
 Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
-// clang-format off
 
 /* Initialize *cv. */
 void nsync_cv_init (nsync_cv *cv) {

third_party/nsync/mem/nsync_debug.c

@@ -26,7 +26,6 @@ asm(".ident\t\"\\n\\n\
 *NSYNC (Apache 2.0)\\n\
 Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
-// clang-format off
 
 /* Routines for debugging. */
 

third_party/nsync/mem/nsync_mu_wait.c

@@ -27,7 +27,6 @@ asm(".ident\t\"\\n\\n\
 *NSYNC (Apache 2.0)\\n\
 Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
-// clang-format off
 
 /* Attempt to remove waiter *w from *mu's
    waiter queue.  If successful, leave the lock held in mode *l_type, and

third_party/nsync/mem/nsync_note.c

@@ -30,7 +30,6 @@ asm(".ident\t\"\\n\\n\
 *NSYNC (Apache 2.0)\\n\
 Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
-// clang-format off
 
 /* Locking discipline for the nsync_note implementation:
 

third_party/nsync/mem/nsync_once.c

@@ -27,7 +27,6 @@ asm(".ident\t\"\\n\\n\
 *NSYNC (Apache 2.0)\\n\
 Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
-// clang-format off
 
 /* An once_sync_s struct contains a lock, and a condition variable on which
    threads may wait for an nsync_once to be initialized by another thread.

third_party/nsync/mem/nsync_sem_wait.c

@@ -28,7 +28,6 @@ asm(".ident\t\"\\n\\n\
 *NSYNC (Apache 2.0)\\n\
 Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
-// clang-format off
 
 /* Wait until one of:
      w->sem is non-zero----decrement it and return 0.

third_party/nsync/mem/nsync_wait.c

@@ -30,7 +30,6 @@ asm(".ident\t\"\\n\\n\
 *NSYNC (Apache 2.0)\\n\
 Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
-// clang-format off
 
 int nsync_wait_n (void *mu, void (*lock) (void *), void (*unlock) (void *),
 		  nsync_time abs_deadline,