Re-enable all the windows warnings except 4267

core/fxcrt/fx_basic_gcc.cpp

Index: core/fxcrt/fx_basic_gcc.cpp
diff --git a/core/fxcrt/fx_basic_gcc.cpp b/core/fxcrt/fx_basic_gcc.cpp
index 1b2f01ec8971165a0b5c640b9e896189f1069a32..c3afe1115b962641d9798c8911d72b92b1455ed2 100644
--- a/core/fxcrt/fx_basic_gcc.cpp
+++ b/core/fxcrt/fx_basic_gcc.cpp
@@ -39,7 +39,10 @@ IntType FXSYS_StrToInt(const CharType* str) {
     num = num * 10 + val;
     str++;
   }
-  return neg ? -num : num;
+  // When it is a negative value, -num should be returned. Since num may be of
+  // unsigned type, use ~num + 1 to avoid the warning of applying unary minus
+  // operator to unsigned type.
+  return neg ? ~num + 1 : num;
 }
 
 template <typename T, typename UT, typename STR_T>