Moved mutex from header to .cpp file, since defining one instance of the mutex for each fiel that includes the download manager is almost certainly not what was intended

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@5675 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/addons/network.cpp

@@ -26,6 +26,8 @@
 
 #include "io/file_manager.hpp"
 
+pthread_mutex_t download_mutex;
+
 NetworkHttp * network_http = 0;
 NetworkHttp::NetworkHttp()
 {

src/addons/network.hpp

@@ -41,6 +41,6 @@ bool download(std::string file, std::string save = "", int * progress_data = 0);
 
 int progressDownload (void *clientp, double dltotal, double dlnow, double ultotal, double ulnow);
 
-static pthread_mutex_t download_mutex;
+extern pthread_mutex_t download_mutex;
 #endif
 #endif