fix building on Win7

CMakeLists.txt

@@ -57,6 +57,16 @@ check_library_exists(m pow "" HAVE_LIBM)
 check_include_file("dirent.h" HAVE_DIRENT_H)
 check_symbol_exists(strcasecmp "strings.h" HAVE_DECL_STRCASECMP)
 check_symbol_exists(strncasecmp "strings.h" HAVE_DECL_STRNCASECMP)
+check_c_source_compiles("
+    #include <windows.h>
+    int main()
+    {
+        CreateWaitableTimerEx(NULL, NULL, CREATE_WAITABLE_TIMER_HIGH_RESOLUTION);
+        return 0;
+    }
+  "
+  HAVE_HIGH_RES_TIMER
+)
 check_c_source_compiles("
     #include <immintrin.h>
     int main()

config.h.in

@@ -6,6 +6,7 @@
 #cmakedefine HAVE_DIRENT_H
 #cmakedefine01 HAVE_DECL_STRCASECMP
 #cmakedefine01 HAVE_DECL_STRNCASECMP
+#cmakedefine HAVE_HIGH_RES_TIMER
 #cmakedefine HAVE__DIV64
 #cmakedefine HAVE_ALSA
 #cmakedefine HAVE_FLUIDSYNTH

src/i_timer.c

@@ -148,11 +148,13 @@ void I_InitTimer(void)
 
 #ifdef _WIN32
     // Create an unnamed waitable timer.
+    hTimer = NULL;
+  #ifdef HAVE_HIGH_RES_TIMER
     hTimer = CreateWaitableTimerEx(NULL, NULL,
                                    CREATE_WAITABLE_TIMER_MANUAL_RESET
                                    | CREATE_WAITABLE_TIMER_HIGH_RESOLUTION,
                                    TIMER_ALL_ACCESS);
-
+  #endif
     if (hTimer == NULL)
     {
         hTimer = CreateWaitableTimer(NULL, TRUE, NULL);