Add KAITAI_STREAM_H_CPP11_SUPPORT macro, fix C++98 compatibility

See #72 (comment)

The standard library header `<type_traits>` is only available since
C++11 (see https://en.cppreference.com/w/cpp/header/type_traits), so we
must not try to include it in C++98 mode.

kaitai/exceptions.h

@@ -11,7 +11,7 @@
 // achieve that: C++98 compilers prefer `throw()`, C++11 and later
 // use `noexcept`. We define KS_NOEXCEPT macro for that.
 
-#if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1900)
+#ifdef KAITAI_STREAM_H_CPP11_SUPPORT
 #define KS_NOEXCEPT noexcept
 #else
 #define KS_NOEXCEPT throw()

kaitai/kaitaistream.h

@@ -16,7 +16,10 @@
 #include <limits> // std::numeric_limits
 #include <sstream> // std::istringstream
 #include <string> // std::string
+
+#ifdef KAITAI_STREAM_H_CPP11_SUPPORT
 #include <type_traits> // std::enable_if, std::is_integral
+#endif
 
 namespace kaitai {
 
@@ -234,8 +237,7 @@ class kstream {
      * since C++11) in older C++ implementations.
      */
     template<typename I>
-// check for C++11 support - https://stackoverflow.com/a/40512515
-#if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1900)
+#ifdef KAITAI_STREAM_H_CPP11_SUPPORT
     // https://stackoverflow.com/a/27913885
     typename std::enable_if<
             std::is_integral<I>::value &&