Update LLVM to latest upstream. (#1080)

Also change header guards to WPI header guards.
Remove StringRef::c_str() customization, replacing the handful of uses with Twine or SmallString.
TCPStream: Include errno.h and make Windows includes lowercase for consistency.

Upstream LLVM version: eb4186cca7924fb1706357545311a2fa3de40c59

wpiutil/src/main/native/cpp/memory.cpp

@@ -0,0 +1,43 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "wpi/memory.h"
+
+#include <exception>
+
+#include "wpi/raw_ostream.h"
+
+namespace wpi {
+
+void* CheckedCalloc(size_t num, size_t size) {
+  void* p = std::calloc(num, size);
+  if (!p) {
+    errs() << "FATAL: failed to allocate " << (num * size) << " bytes\n";
+    std::terminate();
+  }
+  return p;
+}
+
+void* CheckedMalloc(size_t size) {
+  void* p = std::malloc(size == 0 ? 1 : size);
+  if (!p) {
+    errs() << "FATAL: failed to allocate " << size << " bytes\n";
+    std::terminate();
+  }
+  return p;
+}
+
+void* CheckedRealloc(void* ptr, size_t size) {
+  void* p = std::realloc(ptr, size == 0 ? 1 : size);
+  if (!p) {
+    errs() << "FATAL: failed to allocate " << size << " bytes\n";
+    std::terminate();
+  }
+  return p;
+}
+
+}  // namespace wpi