Perform some code maintenance

- Change IDT code so kprintf() isn't mandatory dependency
- Document current intentions around pthread_cancel()
- Make _npassert() an _unassert() in MODE=tiny

third_party/nsync/common.internal.h

@@ -222,11 +222,7 @@ static const uint32_t NSYNC_WAITER_TAG = 0x726d2ba9;
 
 #define CONTAINER(t_, f_, p_) ((t_ *)(((char *)(p_)) - offsetof(t_, f_)))
 
-#ifdef TINY
-#define ASSERT(x) _unassert(x)
-#else
 #define ASSERT(x) _npassert(x)
-#endif
 
 /* Return a pointer to the nsync_waiter_s containing nsync_dll_element_ *e. */
 #define DLL_NSYNC_WAITER(e)                 \

third_party/nsync/mu_semaphore.c

@@ -30,11 +30,7 @@ Copyright 2016 Google, Inc.\\n\
 https://github.com/google/nsync\"");
 // clang-format off
 
-#ifdef TINY
-#define ASSERT(x) _unassert(x)
-#else
 #define ASSERT(x) _npassert(x)
-#endif
 
 /* Check that atomic operations on nsync_atomic_uint32_ can be applied to int. */
 static const int assert_int_size = 1 /