Make checks for <version> C++ specific.

Author: jzmaddock

Diff for: include/boost/config/detail/suffix.hpp

@@ -1202,7 +1202,7 @@ namespace std{ using ::type_info; }
 #endif
 #endif
 
-#ifdef __has_include
+#if defined(__cplusplus) && defined(__has_include)
 #if !__has_include(<version>)
 #  define BOOST_NO_CXX20_HDR_VERSION
 #else

Diff for: include/boost/config/stdlib/libcpp.hpp

@@ -104,7 +104,7 @@
 #  define BOOST_NO_CXX98_BINDERS
 #endif
 
-#ifdef __has_include
+#if defined(__cplusplus) && defined(__has_include)
 #if __has_include(<version>)
 #include <version>