Move entirety of llvm namespace to wpi namespace.

During shared library loading, a different libLLVM can be pulled in, causing
llvm symbols from dependent libraries to resolve to that library instead of
this one. This has been seen in the wild with the Mesa OpenGL implementation
in JavaFX applications (see wpilibsuite/shuffleboard#361).

This is clearly a very breaking change. For some level of backwards
compatibility, a namespace alias from llvm to wpi is performed in the "llvm"
headers.  Unfortunately, forward declarations of llvm classes will still break,
but compilers seem to generate clear error messages in those cases
("namespace alias 'llvm' not allowed here, assuming 'wpi'").

This change also moves all the wpiutil headers to a single "wpi" subdirectory
from the previously split "llvm", "support", "tcpsockets", and "udpsockets".
Shim headers will be added for backwards compatibility in a later commit.

wpiutil/src/main/native/include/wpi/TCPStream.h

@@ -0,0 +1,71 @@
+/*
+   TCPStream.h
+
+   TCPStream class interface. TCPStream provides methods to trasnfer
+   data between peers over a TCP/IP connection.
+
+   ------------------------------------------
+
+   Copyright (c) 2013 [Vic Hargrave - http://vichargrave.com]
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+#ifndef WPIUTIL_TCPSOCKETS_TCPSTREAM_H_
+#define WPIUTIL_TCPSOCKETS_TCPSTREAM_H_
+
+#include <cstddef>
+#include <string>
+
+#include "wpi/NetworkStream.h"
+
+struct sockaddr_in;
+
+namespace wpi {
+
+class TCPStream : public NetworkStream {
+  int m_sd;
+  std::string m_peerIP;
+  int m_peerPort;
+  bool m_blocking;
+
+ public:
+  friend class TCPAcceptor;
+  friend class TCPConnector;
+
+  ~TCPStream();
+
+  size_t send(const char* buffer, size_t len, Error* err) override;
+  size_t receive(char* buffer, size_t len, Error* err,
+                 int timeout = 0) override;
+  void close() override;
+
+  StringRef getPeerIP() const override;
+  int getPeerPort() const override;
+  void setNoDelay() override;
+  bool setBlocking(bool enabled) override;
+  int getNativeHandle() const override;
+
+  TCPStream(const TCPStream& stream) = delete;
+  TCPStream& operator=(const TCPStream&) = delete;
+
+ private:
+  bool WaitForReadEvent(int timeout);
+
+  TCPStream(int sd, sockaddr_in* address);
+  TCPStream() = delete;
+};
+
+}  // namespace wpi
+
+#endif  // WPIUTIL_TCPSOCKETS_TCPSTREAM_H_