libgolang/thread: Don't ignore PyThread_acquire_lock return

With WAIT_LOCK flag and correct usage PyThread_acquire_lock should never
fail, but let's be cautious and verify that it indeed succeeds to acquire
the lock.

The rest of external functions called by thread runtime either have void
return, or their return is checked.

golang/runtime/_runtime_thread.pyx

@@ -112,7 +112,9 @@ cdef nogil:
 
     void sema_acquire(_libgolang_sema *gsema):
         pysema = <PyThread_type_lock>gsema
-        PyThread_acquire_lock(pysema, WAIT_LOCK)
+        ok = PyThread_acquire_lock(pysema, WAIT_LOCK)
+        if ok == 0:
+            panic("pyxgo: thread: sema_acquire: PyThread_acquire_lock failed")
 
     void sema_release(_libgolang_sema *gsema):
         pysema = <PyThread_type_lock>gsema