Auto merge of #2894 - per-gron:dont-export-unless-needed, r=str4d

Make some globals static that can be

I wrote this patch as part of making a Bazel build system but it really is independent from that so I'm putting this as a separate PR.

External linkage does not help and just encourages sloppy dependencies (ie using symbols only declared in a cpp file in some other cpp file) and can lead to weird issues when there are name collisions.

src/util.cpp

@@ -125,7 +125,7 @@ void locking_callback(int mode, int i, const char* file, int line) NO_THREAD_SAF
 }
 
 // Init
-class CInit
+static class CInit
 {
 public:
     CInit()