Replace USE_LOCAL_HEADERS with USE_INTERNAL_*

code/qcommon/ioapi.c

@@ -10,7 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#ifdef USE_LOCAL_HEADERS
+#ifdef USE_INTERNAL_ZLIB
 #include "zlib.h"
 #else
 #include <zlib.h>

code/qcommon/unzip.h

@@ -49,7 +49,7 @@
 extern "C" {
 #endif
 
-#ifdef USE_LOCAL_HEADERS
+#ifdef USE_INTERNAL_ZLIB
   #include "zlib.h"
 #else
   #include <zlib.h>