Add some external dependencies.

extern/EtcLib/Etc/EtcConfig.h

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2015 The Etc2Comp Authors.
+ *
+ * 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.
+ */
+
+#pragma once
+
+#ifdef _WIN32
+#define ETC_WINDOWS (1)
+#else
+#define ETC_WINDOWS (0)
+#endif
+
+#if __APPLE__
+#define ETC_OSX (1)
+#else
+#define ETC_OSX (0)
+#endif
+
+#if __unix__
+#define ETC_UNIX (1)
+#else
+#define ETC_UNIX (0)
+#endif
+
+
+// short names for common types
+#include <stdint.h>
+typedef int8_t i8;
+typedef int16_t i16;
+typedef int32_t i32;
+typedef int64_t i64;
+
+typedef uint8_t u8;
+typedef uint16_t u16;
+typedef uint32_t u32;
+typedef uint64_t u64;
+
+typedef float	f32;
+typedef double	f64;
+
+// Keep asserts enabled in release builds during development
+#undef NDEBUG
+
+// 0=disable. stb_image can be used if you need to compress 
+//other image formats like jpg
+#define USE_STB_IMAGE_LOAD 0	
+
+#if ETC_WINDOWS
+#include <SDKDDKVer.h>
+#define _CRT_SECURE_NO_WARNINGS (1)
+#include <tchar.h>
+#endif
+
+#include <stdio.h>
+