Add early OS X compiling support from @Zorro666 - still non-functional!

* Build with cmake -DENABLE_VULKAN=OFF -DENABLE_QRENDERDOC=OFF

renderdoccmd/renderdoccmd_apple.cpp

@@ -0,0 +1,59 @@
+/******************************************************************************
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Baldur Karlsson
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ ******************************************************************************/
+
+#include <string>
+
+#include <locale.h>
+#include <string.h>
+
+#include <unistd.h>
+
+#include <replay/renderdoc_replay.h>
+
+using std::string;
+
+string GetUsername()
+{
+  char buf[256] = {0};
+  getlogin_r(buf, 255);
+
+  return string(buf, buf + strlen(buf));
+}
+
+void DisplayRendererPreview(ReplayRenderer *renderer, TextureDisplay displayCfg)
+{
+}
+
+int renderdoccmd(int argc, char **argv);
+
+int main(int argc, char *argv[])
+{
+  setlocale(LC_CTYPE, "");
+
+  // do any apple-specific setup here
+
+  // process any apple-specific arguments here
+
+  return renderdoccmd(argc, argv);
+}