fix bug in pack_float and pack_double

Author: GeorgFritze

include/msgpack/v1/pack.hpp

@@ -1143,7 +1143,7 @@ inline packer<Stream>& packer<Stream>::pack_float(float d)
         if(d >= 0 && d <= float(std::numeric_limits<uint64_t>::max()) && d == float(uint64_t(d))) {
             pack_imp_uint64(uint64_t(d));
             return *this;        
-        } else if(d >= float(std::numeric_limits<int64_t>::min()) && d == float(int64_t(d))) {
+        } else if(d < 0 && d >= float(std::numeric_limits<int64_t>::min()) && d == float(int64_t(d))) {
             pack_imp_int64(int64_t(d));
             return *this;
         }
@@ -1165,7 +1165,7 @@ inline packer<Stream>& packer<Stream>::pack_double(double d)
         if(d >= 0 && d <= double(std::numeric_limits<uint64_t>::max()) && d == double(uint64_t(d))) {
             pack_imp_uint64(uint64_t(d));
             return *this;        
-        } else if(d >= double(std::numeric_limits<int64_t>::min()) && d == double(int64_t(d))) {
+        } else if(d < 0 && d >= double(std::numeric_limits<int64_t>::min()) && d == double(int64_t(d))) {
             pack_imp_int64(int64_t(d));
             return *this;
         }