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.
diff --git a/Makefile.in b/Makefile.in
index 7855443..cd137fd 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -103,10 +103,12 @@
 DOCS_HTML := $(DOCS_XML:$(objroot)%.xml=$(srcroot)%.html)
 DOCS_MAN3 := $(DOCS_XML:$(objroot)%.xml=$(srcroot)%.3)
 DOCS := $(DOCS_HTML) $(DOCS_MAN3)
-C_TESTLIB_SRCS := $(srcroot)test/src/math.c $(srcroot)test/src/SFMT.c \
-	$(srcroot)test/src/test.c $(srcroot)test/src/thread.c
+C_TESTLIB_SRCS := $(srcroot)test/src/math.c $(srcroot)test/src/mtx.c \
+	$(srcroot)test/src/SFMT.c $(srcroot)test/src/test.c \
+	$(srcroot)test/src/thd.c
 C_UTIL_INTEGRATION_SRCS := $(srcroot)src/util.c
 TESTS_UNIT := $(srcroot)test/unit/bitmap.c $(srcroot)test/unit/math.c \
+	$(srcroot)test/unit/mq.c $(srcroot)test/unit/mtx.c \
 	$(srcroot)test/unit/SFMT.c $(srcroot)test/unit/tsd.c
 TESTS_INTEGRATION := $(srcroot)test/integration/aligned_alloc.c \
 	$(srcroot)test/integration/allocated.c \