build: Replace AX_CXX_COMPILE_STDCXX_11 with latest AX_CXX_COMPILE_STDCXX

The former appended the necessary switch to enable C++11 to the CXXFLAGS
whereas AX_CXX_COMPILE_STDCXX appends it to CXX which has the benefit
that all C++ sources are compiled using the same C++ standard. Therefore
it is no longer necessary to manually hardcode '-std=c++11' anywhere
like we did in the Ruby bindings linker command and assures that the
compilation of them is done with C++11 support as well.

This fixes bug #795

Author: marv

Makefile.am

@@ -705,7 +705,7 @@ $(ROBJ): $(RWRAP) \
 	$(AM_V_CXX)$(CXX) $(RBSIGROK_CFLAGS) -I. -Iinclude -Ibindings/cxx/include $(local_includes) -fPIC -o $@ -c $<
 
 $(REXT): $(ROBJ) @ORDER@ bindings/cxx/libsigrokcxx.la
-	$(AM_V_CXXLD)$(CXX) -shared -std=c++11 -o $@ $< -lsigrokcxx -Lbindings/cxx/.libs $(RBSIGROK_LIBS)
+	$(AM_V_CXXLD)$(CXX) -shared -o $@ $< -lsigrokcxx -Lbindings/cxx/.libs $(RBSIGROK_LIBS)
 
 ruby-build: $(REXT)
 

configure.ac

@@ -303,7 +303,7 @@ AC_ARG_ENABLE([java],
 sr_cxx_missing=
 
 # Check if the C++ compiler supports the C++11 standard.
-AX_CXX_COMPILE_STDCXX_11([noext], [optional])
+AX_CXX_COMPILE_STDCXX([11], [noext], [optional])
 AS_IF([test "x$HAVE_CXX11" != x1],
 	[SR_APPEND([sr_cxx_missing], [', '], ['C++11'])])