Fix #189 unit test "Column.basis" failing on Visual Studio 2013

The implicit cast to std::string() would fallback to const char* with MSVC 2010-2013 (witch does not work with the NULL char in the middle)

Without it, trying to access a binary blob with implicit cast to string
ends up converting it to a C-style char*, damaging the data by truncating it to the first null character!

appveyor.yml

@@ -23,10 +23,6 @@ environment:
   - arch: Win32
   - arch: Win64
 
-matrix:
-  allow_failures:
-    - image: Visual Studio 2013
-  
 init:
   - echo %APPVEYOR_BUILD_WORKER_IMAGE% - %configuration% - %arch%
   - if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2017" (set vs=Visual Studio 15 2017)

include/SQLiteCpp/Column.h

@@ -224,12 +224,16 @@ public:
         return getBlob();
     }
 
-#if !(defined(_MSC_VER) && _MSC_VER < 1900)
+#if !defined(_MSC_VER) || _MSC_VER >= 1900
     // NOTE : the following is required by GCC and Clang to cast a Column result in a std::string
     // (error: conversion from ‘SQLite::Column’ to non-scalar type ‘std::string {aka std::basic_string<char>}’)
+    // and also required for Microsoft Visual Studio 2015 and newer
     // but is not working under Microsoft Visual Studio 2010, 2012 and 2013
     // (error C2440: 'initializing' : cannot convert from 'SQLite::Column' to 'std::basic_string<_Elem,_Traits,_Ax>'
     //  [...] constructor overload resolution was ambiguous)
+    // WARNING: without it, trying to access a binary blob with implicit cast to string
+    // ends up converting it to a C-style char*, damaging the data by truncating it to the first null character!
+    // (see https://github.com/SRombauts/SQLiteCpp/issues/189 Visual Studio 2013: unit test "Column.basis" failing)
     /**
      * @brief Inline cast operator to std::string
      *

tests/Column_test.cpp

@@ -68,7 +68,11 @@ TEST(Column, basis) {
         const int           integer = query.getColumn(2); // operator int()
         const double        real    = query.getColumn(3); // operator double()
         const void*         pblob   = query.getColumn(4); // operator void*()
-        const std::string   sblob   = query.getColumn(4); // operator std::string() (or const char* with MSVC)
+#if !defined(_MSC_VER) || _MSC_VER >= 1900
+        // This implicit cast should use operator std::string()
+        // but would fallback to const char* with MSVC 2010-2013 (witch does not work with the NULL char in the middle)
+        const std::string   sblob   = query.getColumn(4); // operator std::string()
+#endif
         const void*         pempty  = query.getColumn(5); // operator void*()
         EXPECT_EQ(1,            id1);
         EXPECT_EQ(1,            id2);
@@ -81,8 +85,10 @@ TEST(Column, basis) {
         EXPECT_EQ(-123,         integer);
         EXPECT_EQ(0.123,        real);
         EXPECT_EQ(0,            memcmp("bl\0b", pblob, size));
+#if !defined(_MSC_VER) || _MSC_VER >= 1900
         EXPECT_EQ((size_t)size, sblob.size());
         EXPECT_EQ(0,            memcmp("bl\0b", &sblob[0], size));
+#endif
         EXPECT_EQ(NULL,         pempty);
     }