Merge commits '88be4e8d b4756543 10dab907 58178851 de6af6ae baa26542 2b7337f6 a44a3393 f44c1ebd d543c0d9 43e7b115 7a2fff85 ' into temp-merge-1758

configure.ac

@@ -579,6 +579,14 @@ if test x"$enable_experimental" = x"no"; then
   fi
 fi
 
+# Check for concurrency support (tests only)
+if test "x$enable_tests" != x"no"; then
+  AC_CHECK_HEADERS([sys/types.h sys/wait.h unistd.h])
+  AS_IF([test "x$ac_cv_header_sys_types_h" = xyes && test "x$ac_cv_header_sys_wait_h" = xyes &&
+         test "x$ac_cv_header_unistd_h" = xyes], [TEST_DEFINES="-DSUPPORTS_CONCURRENCY=1"], TEST_DEFINES="")
+  AC_SUBST(TEST_DEFINES)
+fi
+
 ###
 ### Generate output
 ###