Initialize libsodium in the gtest suite.

src/gtest/main.cpp

@@ -1,6 +1,8 @@
 #include "gtest/gtest.h"
+#include "sodium.h"
 
 int main(int argc, char **argv) {
+  assert(sodium_init() != -1);
   testing::InitGoogleTest(&argc, argv);
   return RUN_ALL_TESTS();
 }