Fix game compilation error on non-Windows platforms due to the errno …

…stuff being defined elsewhere.

doomsday/plugins/jdoom/src/m_cheat.c

@@ -32,6 +32,9 @@
 #include <stdlib.h>
 #include <string.h>
 #include <math.h>
+#ifdef UNIX
+# include <errno.h>
+#endif
 
 #include "jdoom.h"
 

doomsday/plugins/jdoom64/src/m_cheat.c

@@ -34,6 +34,9 @@
 #include <string.h>
 #include <stdio.h>
 #include <math.h>
+#ifdef UNIX
+# include <errno.h>
+#endif
 
 #include "jdoom64.h"
 

doomsday/plugins/jheretic/src/m_cheat.c

@@ -33,6 +33,9 @@
 #include <stdio.h>
 #include <string.h>
 #include <math.h>
+#ifdef UNIX
+# include <errno.h>
+#endif
 
 #include "jheretic.h"
 

doomsday/plugins/jhexen/src/m_cheat.c

@@ -33,6 +33,9 @@
 #include <stdio.h>
 #include <string.h>
 #include <math.h>
+#ifdef UNIX
+# include <errno.h>
+#endif
 
 #include "jhexen.h"