Add C++ class example for Guile

Also correct other example c++ makefiles

Examples/guile/class/Makefile

@@ -0,0 +1,18 @@
+TOP        = ../..
+SWIG       = $(TOP)/../preinst-swig
+CXXSRCS    = example.cxx
+TARGET     = example
+INTERFACE  = example.i
+
+check: build
+
+build:
+	$(MAKE) -f $(TOP)/Makefile CXXSRCS='$(CXXSRCS)' SWIG='$(SWIG)' \
+	TARGET='$(TARGET)' INTERFACE='$(INTERFACE)' guile_cpp
+
+static:
+	$(MAKE) -f $(TOP)/Makefile CXXSRCS='$(CXXSRCS)' SWIG='$(SWIG)' \
+	TARGET='my-guile' INTERFACE='$(INTERFACE)' guile_static_cpp
+
+clean:
+	$(MAKE) -f $(TOP)/Makefile TARGET='$(TARGET)' guile_clean