Generate version header when configuring project

The basic idea is we create a version header template at
"src/base/version.h.in" and the build systems are expected to replace
strings that are enclosed with @ symbols and generate
"src/base/version.h" for other source files to consume/include.

src/base/bittorrent/session.cpp

@@ -85,6 +85,7 @@
 #include "base/utils/misc.h"
 #include "base/utils/net.h"
 #include "base/utils/random.h"
+#include "base/version.h"
 #include "bandwidthscheduler.h"
 #include "common.h"
 #include "customstorage.h"