testmathlib.cpp: fixed literal overflow warnings

example:
```
test/testmathlib.cpp:393:43: error: integer constant is so large that it is unsigned [-Werror]
  393 |             constexpr MathLib::bigint i = 18446744073709551615;
      |                                           ^~~~~~~~~~~~~~~~~~~~
```

Author: firewave

test/testmathlib.cpp

@@ -387,22 +387,18 @@ class TestMathLib : public TestFixture {
         ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigNumber("-02000000000000000000000"), INTERNAL, "Internal Error. MathLib::toBigNumber: out_of_range: -02000000000000000000000");
 
         // min/max and out-of-bounds - decimal
-        SUPPRESS_WARNING_CLANG_PUSH("-Wimplicitly-unsigned-literal")
-        SUPPRESS_WARNING_GCC_PUSH("-Woverflow")
         {
-            constexpr MathLib::bigint i = 18446744073709551615;
+            constexpr MathLib::bigint i = 0xffffffff; // 18446744073709551615;
             ASSERT_EQUALS(i, MathLib::toBigNumber(std::to_string(i)));
             ASSERT_EQUALS(i, MathLib::toBigNumber("18446744073709551615"));
         }
         {
-            constexpr MathLib::bigint i = -18446744073709551615;
+            constexpr MathLib::bigint i = 1; // -18446744073709551615;
             ASSERT_EQUALS(i, MathLib::toBigNumber(std::to_string(i)));
             ASSERT_EQUALS(i, MathLib::toBigNumber("-18446744073709551615"));
         }
-        SUPPRESS_WARNING_GCC_POP
-        SUPPRESS_WARNING_CLANG_POP
 
-            ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigNumber("18446744073709551616"), INTERNAL, "Internal Error. MathLib::toBigNumber: out_of_range: 18446744073709551616");
+        ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigNumber("18446744073709551616"), INTERNAL, "Internal Error. MathLib::toBigNumber: out_of_range: 18446744073709551616");
         ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigNumber("-18446744073709551616"), INTERNAL, "Internal Error. MathLib::toBigNumber: out_of_range: -18446744073709551616");
 
         ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigNumber("invalid"), INTERNAL, "Internal Error. MathLib::toBigNumber: invalid_argument: invalid");
@@ -563,22 +559,18 @@ class TestMathLib : public TestFixture {
         ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigUNumber("-02000000000000000000000"), INTERNAL, "Internal Error. MathLib::toBigUNumber: out_of_range: -02000000000000000000000");
 
         // min/max and out-of-bounds - decimal
-        SUPPRESS_WARNING_CLANG_PUSH("-Wimplicitly-unsigned-literal")
-        SUPPRESS_WARNING_GCC_PUSH("-Woverflow")
         {
-            constexpr MathLib::biguint u = 18446744073709551615;
+            constexpr MathLib::biguint u = 0xffffffffffffffff; // 18446744073709551615;
             ASSERT_EQUALS(u, MathLib::toBigUNumber(std::to_string(u)));
             ASSERT_EQUALS(u, MathLib::toBigUNumber("18446744073709551615"));
         }
         {
-            constexpr MathLib::biguint u = -18446744073709551615;
+            constexpr MathLib::biguint u = 1; // -18446744073709551615;
             ASSERT_EQUALS(u, MathLib::toBigUNumber(std::to_string(u)));
             ASSERT_EQUALS(u, MathLib::toBigUNumber("-18446744073709551615"));
         }
-        SUPPRESS_WARNING_GCC_POP
-        SUPPRESS_WARNING_CLANG_POP
 
-            ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigUNumber("18446744073709551616"), INTERNAL, "Internal Error. MathLib::toBigUNumber: out_of_range: 18446744073709551616");
+        ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigUNumber("18446744073709551616"), INTERNAL, "Internal Error. MathLib::toBigUNumber: out_of_range: 18446744073709551616");
         ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigUNumber("-18446744073709551616"), INTERNAL, "Internal Error. MathLib::toBigUNumber: out_of_range: -18446744073709551616");
 
         ASSERT_THROW_INTERNAL_EQUALS(MathLib::toBigUNumber("invalid"), INTERNAL, "Internal Error. MathLib::toBigUNumber: invalid_argument: invalid");