Fix failures on R hub and Win builder. (#7763)

* Update date.
* Workaround amalgamation build with clang. (SimpleDMatrix instantiation)
* Workaround compiler error with driver push.
* Revert autoconf requirement.
* Fix model IO on 32-bit environment. (i386)
* Clarify the function name.

include/xgboost/json_io.h

@@ -182,12 +182,12 @@ T BuiltinBSwap(T v) {
 #endif  //  defined(__GLIBC__)
 
 template <typename T, std::enable_if_t<sizeof(T) == 1>* = nullptr>
-inline T ByteSwap(T v) {
+inline T ToBigEndian(T v) {
   return v;
 }
 
 template <typename T, std::enable_if_t<sizeof(T) != 1>* = nullptr>
-inline T ByteSwap(T v) {
+inline T ToBigEndian(T v) {
   static_assert(std::is_pod<T>::value, "Only pod is supported.");
 #if DMLC_LITTLE_ENDIAN
   auto constexpr kS = sizeof(T);
@@ -217,7 +217,7 @@ class UBJReader : public JsonReader {
   template <typename T>
   T ReadPrimitive() {
     auto v = ReadStream<T>();
-    v = ByteSwap(v);
+    v = ToBigEndian(v);
     return v;
   }