wrap all library code into namespace if VCMI_LIB_NAMESPACE is defined

preparation for having client and server in a single process

lib/vstd/StringUtils.cpp

@@ -1,6 +1,8 @@
 #include "StdInc.h"
 #include <vstd/StringUtils.h>
 
+VCMI_LIB_NAMESPACE_BEGIN
+
 namespace vstd
 {
 
@@ -30,3 +32,5 @@ namespace vstd
 	}
 
 }
+
+VCMI_LIB_NAMESPACE_END