support base argument to math.log

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/MathModuleBuiltins.java

@@ -872,19 +872,24 @@ public double sin(double value) {
         }
     }
 
-    @Builtin(name = "log", fixedNumOfArguments = 1)
+    @Builtin(name = "log", minNumOfArguments = 1, maxNumOfArguments = 2)
     @GenerateNodeFactory
     public abstract static class LogNode extends PythonBuiltinNode {
 
         @Specialization
-        public double log(int value) {
+        public double log(int value, @SuppressWarnings("unused") PNone novalue) {
             return Math.log(value);
         }
 
         @Specialization
-        public double log(double value) {
+        public double log(double value, @SuppressWarnings("unused") PNone novalue) {
             return Math.log(value);
         }
+
+        @Specialization
+        public double log(int value, int base) {
+            return Math.log(value) / Math.log(base);
+        }
     }
 
     @Builtin(name = "fabs", fixedNumOfArguments = 1)