Drop uint 256 not operator

All the other operators are integer or bit operations, and this is unused
apart from tests.

Author: Empact

src/arith_uint256.h

@@ -64,14 +64,6 @@ class base_uint
 
     explicit base_uint(const std::string& str);
 
-    bool operator!() const
-    {
-        for (int i = 0; i < WIDTH; i++)
-            if (pn[i] != 0)
-                return false;
-        return true;
-    }
-
     const base_uint operator~() const
     {
         base_uint ret;

src/test/arith_uint256_tests.cpp

@@ -198,13 +198,6 @@ BOOST_AUTO_TEST_CASE( shifts ) { // "<<"  ">>"  "<<="  ">>="
 
 BOOST_AUTO_TEST_CASE( unaryOperators ) // !    ~    -
 {
-    BOOST_CHECK(!ZeroL);
-    BOOST_CHECK(!(!OneL));
-    for (unsigned int i = 0; i < 256; ++i)
-        BOOST_CHECK(!(!(OneL<<i)));
-    BOOST_CHECK(!(!R1L));
-    BOOST_CHECK(!(!MaxL));
-
     BOOST_CHECK(~ZeroL == MaxL);
 
     unsigned char TmpArray[32];