Make many more utility classes/headers public. (#76)

Moving these headers from src to include enables other libraries to use the
functionality provided.

* tcpsockets
* atomic_static
* raw_istream
* timestamp
* SafeThread
* Base64
* LEB128
* ConcurrentQueue

The classes have been moved into the wpi namespace as they're generic.

src/ntcore_c.cpp

@@ -10,6 +10,7 @@
 #include <cassert>
 #include <cstdlib>
 
+#include "support/timestamp.h"
 #include "Value_internal.h"
 
 using namespace nt;
@@ -405,6 +406,10 @@ const char *NT_LoadPersistent(const char *filename,
  * Utility Functions
  */
 
+unsigned long long NT_Now() {
+  return wpi::Now();
+}
+
 void NT_SetLogger(NT_LogFunc func, unsigned int min_level) {
   nt::SetLogger(func, min_level);
 }