Fix the recursively included issue for srs_core_time.hpp (ossrs#3159)

* Update srs_core_time.hpp

In included file: main file cannot be included recursively when building a preambleclang(pp_including_mainfile_in_preamble)
srs_core.hpp(43, 10): Error occurred here

* Update srs_core_time.hpp

Reference to trunk/src/protocol/srs_protocol_http_stack.hpp
  (!defined(_MSC_VER) || _MSC_VER<1600) && !defined(__WINE__)
typedef __int8 int8_t;
typedef unsigned __int8 uint8_t;
typedef __int16 int16_t;
typedef unsigned __int16 uint16_t;
typedef __int32 int32_t;
typedef unsigned __int32 uint32_t;
typedef __int64 int64_t;
typedef unsigned __int64 uint64_t;

trunk/src/core/srs_core_time.hpp

@@ -7,10 +7,14 @@
 #ifndef SRS_CORE_TIME_HPP
 #define SRS_CORE_TIME_HPP
 
-#include <srs_core.hpp>
-
 // Time and duration unit, in us.
+#if defined(_WIN32) && !defined(__MINGW32__) && (!defined(_MSC_VER) || _MSC_VER<1600) && !defined(__WINE__)
+#include <BaseTsd.h>
+typedef __int64 srs_utime_t;
+#else
+#include <stdint.h>
 typedef int64_t srs_utime_t;
+#endif
 
 // The time unit in ms, for example 100 * SRS_UTIME_MILLISECONDS means 100ms.
 #define SRS_UTIME_MILLISECONDS 1000