Move common utility classes to wpiutil library. (#79)

This is a breaking change to dependencies that use the static ntcore
library.  Unless the wpiutil library is also linked, linker errors will
result.  This does not affect the shared ntcore library.

src/support/raw_socket_istream.cpp

@@ -0,0 +1,26 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2015. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "support/raw_socket_istream.h"
+
+using namespace wpi;
+
+bool raw_socket_istream::read(void* data, std::size_t len) {
+  char* cdata = static_cast<char*>(data);
+  std::size_t pos = 0;
+
+  while (pos < len) {
+    NetworkStream::Error err;
+    std::size_t count =
+        m_stream.receive(&cdata[pos], len - pos, &err, m_timeout);
+    if (count == 0) return false;
+    pos += count;
+  }
+  return true;
+}
+
+void raw_socket_istream::close() { m_stream.close(); }