Merge pull request #2321 from armink/lts-v3.1.x

Add rt_uint64_t/rt_int64_t type definition.

Author: BernardXiong

include/rtdef.h

@@ -56,9 +56,11 @@ extern "C" {
 typedef signed   char                   rt_int8_t;      /**<  8bit integer type */
 typedef signed   short                  rt_int16_t;     /**< 16bit integer type */
 typedef signed   long                   rt_int32_t;     /**< 32bit integer type */
+typedef signed long long                rt_int64_t;     /**< 64bit integer type */
 typedef unsigned char                   rt_uint8_t;     /**<  8bit unsigned integer type */
 typedef unsigned short                  rt_uint16_t;    /**< 16bit unsigned integer type */
 typedef unsigned long                   rt_uint32_t;    /**< 32bit unsigned integer type */
+typedef unsigned long long              rt_uint64_t;    /**< 64bit unsigned integer type */
 typedef int                             rt_bool_t;      /**< boolean type */
 
 /* 32bit CPU */