cmake: Use SEXP_64BIT on Win64

Do not override SEXP_64BIT on Win64 as now we have custom-long-long for
it.

CMakeLists.txt

@@ -32,17 +32,6 @@ else()
     add_definitions(-DSEXP_USE_DL=0)
 endif()
 
-if(CMAKE_SIZEOF_VOID_P EQUAL 8)
-    if(MSVC)
-        # On MSVC, SEXP_64_BIT is not supported for now (#438)
-        add_definitions(-DSEXP_64_BIT=0)
-    else()
-        add_definitions(-DSEXP_64_BIT=1)
-    endif()
-elseif(CMAKE_SIZEOF_VOID_P EQUAL 4)
-    add_definitions(-DSEXP_64_BIT=0)
-endif()
-
 if(HAVE_STDINT_H)
     add_definitions(-DSEXP_USE_INTTYPES=1)
 endif()

include/chibi/sexp.h

@@ -209,10 +209,6 @@ enum sexp_types {
 #endif
 
 #ifdef _WIN32
-#if defined(_MSC_VER) && SEXP_64_BIT
-/* On SEXP_64_BIT, 128bits arithmetic is mandatory */
-#error Unsupported configuration
-#endif
 #if SEXP_64_BIT
 typedef unsigned int sexp_tag_t;
 typedef unsigned long long sexp_uint_t;