Add mq (message queue) to test infrastructure.

Add mtx (mutex) to test infrastructure, in order to avoid bootstrapping
complications that would result from directly using malloc_mutex.

Rename test infrastructure's thread abstraction from je_thread to thd.

Fix some header ordering issues.

test/src/mtx.c

@@ -0,0 +1,62 @@
+#include "test/jemalloc_test.h"
+
+bool
+mtx_init(mtx_t *mtx)
+{
+
+#ifdef _WIN32
+	if (!InitializeCriticalSectionAndSpinCount(&mtx->lock, _CRT_SPINCOUNT))
+		return (true);
+#elif (defined(JEMALLOC_OSSPIN))
+	mtx->lock = 0;
+#else
+	pthread_mutexattr_t attr;
+
+	if (pthread_mutexattr_init(&attr) != 0)
+		return (true);
+	pthread_mutexattr_settype(&attr, MALLOC_MUTEX_TYPE);
+	if (pthread_mutex_init(&mtx->lock, &attr) != 0) {
+		pthread_mutexattr_destroy(&attr);
+		return (true);
+	}
+	pthread_mutexattr_destroy(&attr);
+#endif
+	return (false);
+}
+
+void
+mtx_fini(mtx_t *mtx)
+{
+
+#ifdef _WIN32
+#elif (defined(JEMALLOC_OSSPIN))
+#else
+	pthread_mutex_destroy(&mtx->lock);
+#endif
+}
+
+void
+mtx_lock(mtx_t *mtx)
+{
+
+#ifdef _WIN32
+	EnterCriticalSection(&mtx->lock);
+#elif (defined(JEMALLOC_OSSPIN))
+	OSSpinLockLock(&mtx->lock);
+#else
+	pthread_mutex_lock(&mtx->lock);
+#endif
+}
+
+void
+mtx_unlock(mtx_t *mtx)
+{
+
+#ifdef _WIN32
+	LeaveCriticalSection(&mtx->lock);
+#elif (defined(JEMALLOC_OSSPIN))
+	OSSpinLockUnlock(&mtx->lock);
+#else
+	pthread_mutex_unlock(&mtx->lock);
+#endif
+}