fixing abs ambiguity compiler error

wjwwood · wjwwood · commit 695a4a57f832 · 2017-04-26T13:37:31.000-07:00
diff --git a/libstage/world.cc b/libstage/world.cc
@@ -86,6 +86,9 @@
 #include <cmath>
 using std::abs;
 
+#include <cstdlib>
+
+#include <stdlib.h>
 #include <assert.h>
 #include <libgen.h> // for dirname(3)
 #include <limits.h>
