core/msg_bus: fix shift on 8-bit platforms
The previous shift would wrap if the compiler defaults to 16 bit words.
Use explicit `unsigned long` integer constants to mitigate that.
before:
2020-07-22 15:25:17,063 # THREAD 1 start
2020-07-22 15:25:17,063 # THREAD 2 start
2020-07-22 15:25:17,065 # THREAD 3 start
2020-07-22 15:25:17,066 # THREADS CREATED
2020-07-22 15:25:17,068 # Posted event 22 to 0 threads
2020-07-22 15:25:17,071 # Posted event 23 to 0 threads
2020-07-22 15:25:17,076 # Posted event 24 to 0 threads
2020-07-22 15:25:17,076 # SUCCESS
2020-07-22 15:26:00,188 # Exiting Pyterm
after:
2020-07-22 15:26:10,374 # THREAD 1 start
2020-07-22 15:26:10,374 # THREAD 2 start
2020-07-22 15:26:10,377 # THREAD 3 start
2020-07-22 15:26:10,377 # THREADS CREATED
2020-07-22 15:26:10,380 # Posted event 22 to 0 threads
2020-07-22 15:26:10,383 # T1 recv: Hello Threads! (type=23)
2020-07-22 15:26:10,386 # T3 recv: Hello Threads! (type=23)
2020-07-22 15:26:10,388 # Posted event 23 to 2 threads
2020-07-22 15:26:10,391 # T2 recv: Hello Threads! (type=24)
2020-07-22 15:26:10,394 # Posted event 24 to 1 threads
2020-07-22 15:26:10,396 # SUCCESS
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