Fix to make os_thread_id it compiled on windows.

sql/sql_class.cc

@@ -2073,7 +2073,7 @@ bool THD::store_globals()
   */
   mysys_var->id= thread_id;
 #ifdef __NR_gettid
-  os_thread_id= syscall(__NR_gettid);
+  os_thread_id= (uint32)syscall(__NR_gettid);
 #else
   os_thread_id= 0;
 #endif

sql/sql_class.h

@@ -2630,7 +2630,7 @@ class THD :public Statement,
   ulong      query_plan_fsort_passes; 
   pthread_t  real_id;                           /* For debugging */
   my_thread_id  thread_id;
-  pid_t      os_thread_id;
+  uint32      os_thread_id;
   uint	     tmp_table, global_disable_checkpoint;
   uint	     server_status,open_options;
   enum enum_thread_type system_thread;

sql/sql_show.cc

@@ -2334,7 +2334,7 @@ class thread_info :public ilink {
   { TRASH(ptr, size); }
 
   ulong thread_id;
-  ulong os_thread_id;
+  uint32 os_thread_id;
   ulonglong start_time;
   uint   command;
   const char *user,*host,*db,*proc_info,*state_info;