Fix clang -std=c99 compilation

PUBLISHED_FROM=fc3f24d40f92f206e5de4a2fd15100430db87717

mongoose.c

@@ -684,6 +684,33 @@ double cs_time() {
   return now;
 }
 #ifdef MG_MODULE_LINES
+#line 1 "./src/../../common/cs_endian.h"
+#endif
+/*
+ * Copyright (c) 2014-2016 Cesanta Software Limited
+ * All rights reserved
+ */
+
+#ifndef CS_COMMON_CS_ENDIAN_H_
+#define CS_COMMON_CS_ENDIAN_H_
+
+/*
+ * clang with std=-c99 uses __LITTLE_ENDIAN, by default
+ * while for ex, RTOS gcc - LITTLE_ENDIAN, by default
+ * it depends on __USE_BSD, but let's have everything
+ */
+#if !defined(BYTE_ORDER) && defined(__BYTE_ORDER)
+#define BYTE_ORDER __BYTE_ORDER
+#ifndef LITTLE_ENDIAN
+#define LITTLE_ENDIAN __LITTLE_ENDIAN
+#endif /* LITTLE_ENDIAN */
+#ifndef BIG_ENDIAN
+#define BIG_ENDIAN __LITTLE_ENDIAN
+#endif /* BIG_ENDIAN */
+#endif /* BYTE_ORDER */
+
+#endif /* CS_COMMON_CS_ENDIAN_H_ */
+#ifdef MG_MODULE_LINES
 #line 1 "./src/../../common/md5.c"
 #endif
 /*