libxx: Add exception specifier to operator delete

CXX:  libxx_delete.cxx
libxx_delete.cxx:52:6: error: 'operator delete' is missing exception
      specification 'throw()' [-Werror,-Wmissing-exception-spec]
void operator delete(FAR void *ptr)
     ^
                                    throw()
1 error generated.

libs/libxx/libxx_delete.cxx

@@ -49,7 +49,7 @@
 // Name: delete
 //***************************************************************************
 
-void operator delete(FAR void *ptr)
+void operator delete(FAR void *ptr) throw()
 {
   lib_free(ptr);
 }

libs/libxx/libxx_deletea.cxx

@@ -49,7 +49,7 @@
 // Name: delete[]
 //***************************************************************************
 
-void operator delete[](FAR void *ptr)
+void operator delete[](FAR void *ptr) throw()
 {
   lib_free(ptr);
 }