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/HttpUtil.h

@@ -0,0 +1,148 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2016-2018 FIRST. 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#ifndef WPIUTIL_SUPPORT_HTTPUTIL_H_
+#define WPIUTIL_SUPPORT_HTTPUTIL_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "wpi/ArrayRef.h"
+#include "wpi/NetworkStream.h"
+#include "wpi/SmallString.h"
+#include "wpi/SmallVector.h"
+#include "wpi/StringMap.h"
+#include "wpi/StringRef.h"
+#include "wpi/Twine.h"
+#include "wpi/raw_istream.h"
+#include "wpi/raw_socket_istream.h"
+#include "wpi/raw_socket_ostream.h"
+
+namespace wpi {
+
+// Unescape a %xx-encoded URI.
+// @param buf Buffer for output
+// @param error Set to true if an error occurred
+// @return Escaped string
+StringRef UnescapeURI(const Twine& str, SmallVectorImpl<char>& buf,
+                      bool* error);
+
+// Escape a string with %xx-encoding.
+// @param buf Buffer for output
+// @param spacePlus If true, encodes spaces to '+' rather than "%20"
+// @return Escaped string
+StringRef EscapeURI(const Twine& str, SmallVectorImpl<char>& buf,
+                    bool spacePlus = true);
+
+// Parse a set of HTTP headers.  Saves just the Content-Type and Content-Length
+// fields.
+// @param is Input stream
+// @param contentType If not null, Content-Type contents are saved here.
+// @param contentLength If not null, Content-Length contents are saved here.
+// @return False if error occurred in input stream
+bool ParseHttpHeaders(raw_istream& is, SmallVectorImpl<char>* contentType,
+                      SmallVectorImpl<char>* contentLength);
+
+// Look for a MIME multi-part boundary.  On return, the input stream will
+// be located at the character following the boundary (usually "\r\n").
+// @param is Input stream
+// @param boundary Boundary string to scan for (not including "--" prefix)
+// @param saveBuf If not null, all scanned characters up to but not including
+//     the boundary are saved to this string
+// @return False if error occurred on input stream, true if boundary found.
+bool FindMultipartBoundary(wpi::raw_istream& is, StringRef boundary,
+                           std::string* saveBuf);
+
+class HttpLocation {
+ public:
+  HttpLocation() = default;
+  HttpLocation(const Twine& url_, bool* error, std::string* errorMsg);
+
+  std::string url;       // retain copy
+  std::string user;      // unescaped
+  std::string password;  // unescaped
+  std::string host;
+  int port;
+  std::string path;  // escaped, not including leading '/'
+  std::vector<std::pair<std::string, std::string>> params;  // unescaped
+  std::string fragment;
+};
+
+class HttpRequest {
+ public:
+  HttpRequest() = default;
+
+  explicit HttpRequest(const HttpLocation& loc)
+      : host{loc.host}, port{loc.port} {
+    SetPath(loc.path, loc.params);
+    SetAuth(loc);
+  }
+
+  template <typename T>
+  HttpRequest(const HttpLocation& loc, const T& extraParams);
+
+  HttpRequest(const HttpLocation& loc, StringRef path_)
+      : host{loc.host}, port{loc.port}, path{path_} {
+    SetAuth(loc);
+  }
+
+  template <typename T>
+  HttpRequest(const HttpLocation& loc, StringRef path_, const T& params)
+      : host{loc.host}, port{loc.port} {
+    SetPath(path_, params);
+    SetAuth(loc);
+  }
+
+  SmallString<128> host;
+  int port;
+  std::string auth;
+  SmallString<128> path;
+
+ private:
+  void SetAuth(const HttpLocation& loc);
+  template <typename T>
+  void SetPath(StringRef path_, const T& params);
+
+  template <typename T>
+  static StringRef GetFirst(const T& elem) {
+    return elem.first;
+  }
+  template <typename T>
+  static StringRef GetFirst(const StringMapEntry<T>& elem) {
+    return elem.getKey();
+  }
+  template <typename T>
+  static StringRef GetSecond(const T& elem) {
+    return elem.second;
+  }
+};
+
+class HttpConnection {
+ public:
+  HttpConnection(std::unique_ptr<wpi::NetworkStream> stream_, int timeout)
+      : stream{std::move(stream_)}, is{*stream, timeout}, os{*stream, true} {}
+
+  bool Handshake(const HttpRequest& request, std::string* warnMsg);
+
+  std::unique_ptr<wpi::NetworkStream> stream;
+  wpi::raw_socket_istream is;
+  wpi::raw_socket_ostream os;
+
+  // Valid after Handshake() is successful
+  SmallString<64> contentType;
+  SmallString<64> contentLength;
+
+  explicit operator bool() const { return stream && !is.has_error(); }
+};
+
+}  // namespace wpi
+
+#include "HttpUtil.inl"
+
+#endif  // WPIUTIL_SUPPORT_HTTPUTIL_H_