Add xmalloc()-like functionality.

xmalloc is a non-standard extension forcing malloc() to
abort should the memory allocation failed instead of returning a
null pointer. Such functionality is quite useful as it provides one
single point of error handling if the caller of malloc() does not
check the result (as it often does!) and segfault is ocurring somewhere
else. If more fine-grained control is necessary one could register a custom
error handler, however, this might not be an option while interposing.

src/options.c

@@ -348,6 +348,11 @@ static void mi_error_default(int err) {
     abort();
   }
 #endif
+#if defined(MI_XMALLOC)
+  if (err==ENOMEM || err==EOVERFLOW) { // abort on memory allocation fails in xmalloc mode
+    abort();
+  }
+#endif
 }
 
 void mi_register_error(mi_error_fun* fun, void* arg) {