libaxx: remove a warning

Change-Id: I0d59ee19258e63d92adc870bb068f733adf39376

libaxx/src/new.cpp

@@ -1,9 +1,11 @@
 #include <stdlib.h>
 
+// See the C++ standard, section 3.7.4 for those definitions
+
 void * operator new (unsigned int size) {
   return malloc(size);
 }
 
-void operator delete (void * ptr) {
+void operator delete (void * ptr) noexcept {
   free(ptr);
 }