[master] workaround for missing initializer for boost posix_time

I did this instead of upgrading boost or changing gcc.

We do the same thing in six other Makefiles.

This will fix failure noticed on NetBSD.

src/lib/asiolink/tests/Makefile.am

@@ -10,6 +10,12 @@ if USE_STATIC_LINK
 AM_LDFLAGS = -static
 endif
 
+# Some versions of GCC warn about some versions of Boost regarding
+# missing initializer for members in its posix_time.
+# https://svn.boost.org/trac/boost/ticket/3477
+# But older GCC compilers don't have the flag.
+AM_CXXFLAGS += $(WARNING_NO_MISSING_FIELD_INITIALIZERS_CFLAG)
+
 CLEANFILES = *.gcno *.gcda
 
 TESTS =