Fix compiler errors

lib/mathlib.cpp

@@ -38,6 +38,8 @@
 #define ISNAN(x)      (std::isnan(x))
 #endif
 
+const int MathLib::bigint_bits = 64;
+
 MathLib::value::value(const std::string &s) :
     intValue(0), doubleValue(0), isUnsigned(false)
 {

lib/mathlib.h

@@ -68,6 +68,7 @@ public:
 
     typedef long long bigint;
     typedef unsigned long long biguint;
+    static const int bigint_bits;
 
     static bigint toLongNumber(const std::string & str);
     static biguint toULongNumber(const std::string & str);