pthread_rwlock_tryrdlock
========================

POSIX specification:
 https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_tryrdlock.html

Gnulib module: pthread-rwlock

Portability problems fixed by Gnulib:

  * This function is missing on some platforms: Minix 3.1.8, mingw, MSVC 14, Android 4.3. But the provided replacement is just a dummy on some of these platforms: Minix 3.1.8.

Portability problems not fixed by Gnulib:

  * This function prefers readers to writers (meaning, when this function is called on an rwlock that is already taken by one or more readers, and another writer is already waiting to take it, this function may return successfully immediately) -- a behaviour that may lead to writer starvation -- on some platforms: glibc 2.28.