math.h may define log2() as a macro; undefine it

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@41530 15284696-431f-4ddb-bdfa-cd5b030d7da7

include/iostream/minmaxheap.h

@@ -42,6 +42,10 @@
 #include <stdlib.h>
 #include <math.h>
 
+#ifdef log2
+#undef log2
+#endif
+
 #include <sstream>
 using namespace std;